I think Syla briefly mentioned that in the memory dream, that the Mc's physical growth was a result of his powers bringing out what was already inside him. I believe that was referring to his unfulfilled genetic potential. Combine that with the idea people have been floating around, about how becoming superhuman brings you to your peak physical state, then I think I have an explanation for the reasons why superhumans look different. First, people like Alice, Micheal, and Met all grew up with parents who gave them all kinds of growth enhancing serums, including that Tanos experimental serum, that unlocked their hidden potential, which was then cultivated to their physical peak from continuous training from childhood and battlefield experience. Which is why they experienced no physical growth.
Tiffany said her breast grew a little bigger, so she did experience some physical growth even if it was minor. Michael said Dexter said his daughters were well trained, so if you combine that with a strict diet, because I feel that's something Dexter would do, and very good genetics, it will explain why Tiffany didn't change much.
In the case of Nathan and Rina, the two of them worked in professions where pushing their bodies to the limit increased their chances of living. So, if we assume that they didn't have any hidden genetic potential, then their natural peak would be when they were a solider and assassin before their crippling injuries.
Now when it comes to Ella's kids since they turned very young, Xanthe mentioned children have trouble enduring their ascension and adjusting to their powers, so I think their physical growth was put off until they were able to gain a harmony of body and mind with their powers included in the mix. I think the fact that they basically become young adults at the limit breaker stage, which involves breaking the limits, and restriction on their powers, showcases that they will go through more pronounced physical growth, because they have completely acclimated to their powers and unlocked their potential up to that point.
Now in the case of the Jake, he was so overweight that I wouldn't be surprised if he had health problems before becoming a superhuman. I don't know it that was a genetic issue or because he never took care of his health, but it doesn't change the fact he looked he was very far from the average physical ability for people his age, much less his peak potential. Which explains his drastic changes.
Finally, in the case of the Mc, before Syla dragged him into the Otherworld, he was standing in front of Indra, as the fucker saturated the room to the brim in his hostile monster energy to the point even level 3 was paralyzed by the memory, who knows if that had any negative effect on his young body. Not to mention, that Syla modified his memories during the most traumatic moment of his life up to that. Even in ordinary humans the mind can cause physical effects on the body with extreme enough circumstances. Or maybe the Mc had to pay a price for hosting the eye as a human, there's a lot of reasons why the mc went through such massive changes when he became a superhuman.
My two cents on this:
I don't think the MC's Physical Growth/Changes were extraordinary in the slightest.
The MC was a Short and Skinny little fucker. When he became a Superhuman, his New Default Body was this Ridiculous Tall, Muscular, and Monster Cocked Man now. And while it's true that Superhuman Transformations seem to bring out the Peak Physical/Fertile Condition of a Human, I don't think the MC's was any more Drastic than someone like Jake.
I agree with the Alice, Michael, and Tiffany though. Their Growth/Change (Physically Speaking), was next to NOTHING, even with Further Evolutions (Michael MAYBE got a bit Bulker and Taller???). As opposed to Jake who Noticeably got even better between Evolution 1 and Evolution 2. This is obviously due to the Serum they were given GROWING UP (Key Word), as we know Ella's Kids, or rather, Humans in General (Like Charlie) who are Transformed into Superhumans at a Young Age (Like Charlie) have a Ridiculous Growth Spurt not only Physically, but in their Abilities as well.
It's strange, because the MC SHOULD have every Characteristic to go with being a Prodigy or Outlier in the Superhuman field, but if you look at the Alternatives, he's really nothing Special so far.
-Henri is Cracked, with an Apparent God Progenitor, and got to Level 5 in like a Week.
-Several Superhumans in H.E.R.O. have reached Level 3 and 4, despite it apparently being 'Rare'.
-Jake and Others had FARRR more Potential on Ella's List, be it from Compatibility, Overall Potential, or whatever than the MC.
-Bernhardt and Malik despite not really having a God Tier Power have all reached the Pinnacle of Level 5, so much so that a Chosen who can mop up 2 Level 5s at once can't even scratch them.
-Jared became a Superhuman like what? A Month ago? And was probably Babied without Combat Experience the entire time and STILL got to Level 4...
-Alice, Deryl, Michael have all been keeping up, even Amber and Liz got a cracked ass Ability.
-The S.I.N Twins are Ridiculous.
The list just goes on, there are plenty of Regular People that are just Significantly better than him, with HALF the Actual Experience and Near-Death Scenarios. And yet again; the MC still has all the hallmarks of being an Outlier such as:
-Getting Infected by 2 Twin Apostles, and Retaining Both Traits Simultaneously.
-Being Born from a Natural Monster Mother at the CHOSEN Level, with the Human Adaptability of his Human Father. So he's Basically Already had Monster DNA (Like the Serum's Injected into the Rich Kids), since Birth.
-Has had the Eye apparently since before even the Syla/Indra Event, according to it at least, it's ALWAYS been with us, just Dormant until we became a Superhuman.
Those are all, so far, Unique Factors that sets him apart from the Average Human, hell, even the Entire Cast so far, and yet - we have nothing to show for it. None of it has made a difference compared to the Lucky Few in the Superhuman World.
Anyway, I know I diverged from the Main Point, but this kind of Topic always drives me back to what Jake asked us on the Beach all those Years ago; "Do you think you're special?" And honestly? No, not right now, I don't think we're any different from the Countless Superhumans in the World. Which is a damn shame, because by every right, we should be. Take away the Reputation of being the Mascot H.E.R.O./Vigilante of the World and, what are we?
