So thumb back about 100 pages and read forward. We have been dissecting this and other things for a while now.
In order to know how powerful the blood is, you need to have a certain aptitude for it. In VtM the Tremere had to perform Thaumaturgy to know details about someone's vitae and or lineage. Virgil, possibly the Princeps, the Feral Nos and of course Fabian are the only ones who have reason to be concerned and or have some knowledge of the power in the blood of the MC. The Princeps is only possibly. He is likely the equivalent of a Ventrue type of vampire, like Sharon likely is, and as a result, would only know how powerful the MC is through trial and error with his powers. Sharon was able to stop the MC from running when they frenzied due to Captain Flamethrower, but I actually think that was some license with the powers if they are semi lifting them from VtM as it should not have worked on him. It is possible that his generation and it effectively blocking her domination would only apply if he is in control of himself, which clearly he wasn't.
Similarly the Princeps would have to have his powers fail against the MC in order to really know, unless he has like beyond Ace Ventura deductive logic and sense of smell. The Feral Nos got it from the blood sweat most likely. As everyone was nervous and she was attacking the MC and very close to him.
As for no one knowing about Calisto, we currently believe one of a couple plausible theories. If the Ancient is a Greek Goddess as we suspect (the being which inspired the myths is what I mean) then it has been put forth that we call her Artemis, as that goddess had a hierea or High Priestess Named Calisto, who was a nymph, pledged to be virginal, seduced by Zeus, cursed by Hera to have a Bear form. Her child from Zeus named Arcus hunted her and nearly killed her not recognizing her in the bear form. That is the Iliad version (by Homer and or Virgil and or Plubius).
Fabian remarks his surprise that she created another childe, indicating that perhaps her prior venture in vampiric reproduction was not without it's bumps. So we presume that the MC is her second actual childe, the first being the problematic Arcus.
She is presumably the childe of Artemis, and if Artemis is a founder of her bloodline, that would make Calisto 4th generation equivalent from VtM. If Artemis is a very ancient Methuselah instead, that makes Calisto 5th generation. The MC is of course 1 generation higher. I did a genealogy for this bloodline and Fabian's based purely on conjecture and Greek mythology.
I believe Calisto to be a 4th generation rather than a 5th generation Ancient Methuselah (both are correct usages of the term) and Artemis to be a bloodline founder, with Zeus as her sire and Cronus as the Titan sire of Zeus. There are lots of possible permutations for bloodlines, and it could be that the whole Greek goddess thing is a red herring, but it would be so much better if it is actually following that rather than the VtM type of Old Testament type crap. (as I had pointed out earlier, Mark Rein-Hagen the creator of VtM is agnostic at best, and most likely an atheist so it is funny how his creation sort of evolved from the Jewish and Christian faiths. In fairness he was brought up in a Christian home so thematically it must have made some sense to him to follow this route)
In any case, I digressed a bit- Calisto is very adept at hiding who she is, to the point that Fabian doesn't even want her name mentioned and for sure that the MC is not associated with her as that would paint a huge target on his back. Now it might be that some Anne Rice made it in to this as well, since Calisto has not diluted her gift overly much, so her childe would be exceptionally gifted. If that and "normal" VtM type stuff applies, the MC is becoming a true beast of a vampire just as Lestat did. Very Quickly. Fabian may not realize it, and most likely no one else but Virgil has a clue, but the MC may already be powerful enough to take out multiple enemies if needed. His Claws certainly are effective, and if you played with your axe in Sharon's meditation room your Prowess is 30 or so. Pretty crazy for a vamp less than 2 months into his career, with scores of 25 in stealth and depending on if you hit all your marks or not, a 13-25 Charisma making that Whisper very potent as well.
Combine that with the visions, the celerity, the ability to outpump blood pool points and the enhanced senses to detect enemies and you have one very scary non fledgling elder type thing in a fledgling's clothing. Calisto is even more so, and can definitely hid in her temple of Pagan Pantheists. I doubt that anyone in the city other than Calisto's folks actually know that much about Calisto, and even then they do not know it all.
I can't insert the quote for some reason. The Feral Nos only said powerful blood and tasty. No other comments to be shared. Fabian knows who the MC is. Virgil thinks that the MC is more than he appears, and the Princeps thinks that the MC is the enthralled lover of his newest Archon. That limited knowledge as has been stated above is the only reason that no one broke bad at the Investiture. I do not think the MC would have died though. Sharon probably would have, as she would have defended him, but Fabian would have defended him rather than face a pissed off Calisto or worse Artemis. So I think he would have gotten away and would have killed some shit on the way out. But that would have wrecked the build up and the whole formula of writing a story!!!!
So yeah, back to my point, Calisto can hide it. So can the MC unless he is faced with a highly sensitive opponent who can sniff him out so to speak.
Anyhow Peace y'all