I am not gonna lie, that seems like a stretch on several points.
1) Though Henri posses the strength of a long forgotten deity, it's "born anew". Could it not mean that he simply fulfilled the same conditions for getting that power, without being chosen by anything conscious?
2) Why the assumption that the only way to equal the aforementioned strength is by being chosen by something? Couldn't Bernhardt and maybe Malik simply be gigachads whose strength grew to equal gods by their own efforts?
All in all, that seems like a fair theory, but I wouldn't say it's "definitely" true.
Won't disagree. Personally I don't care about the idea of "Chosen" that much. It seems like a lose title anyway. For example Aos is the Chosen of Ether, and Ether wants Alice to kill him and inherit Space. It's not like being a "Chosen" means much in the grand scheme of things, at least as far as we've seen. At most it may have to do with getting some gift from your patron (like Valravn), getting some extra knowledge (like Ella? not sure about this but there are indications) etc.
Thing is, that these "gifts" are the most tangible things we have in order to speculate on what being a "Chosen" means and that's thin anyway. So basically, unless we gain some new info, the big Trio being gifted power above their "station" is as good as any.
For your points specifically,
1) Henri is the inheritor of the same power that the king of Seahumans possessed. This is probably what the "born anew" was referring to, in a sense of "The power died with the Seahuman king, but it's born anew with Henri". Funny thing is that the eye calls him "Ascendant, yet still unborn". Also don't forget that Henri literally reached level 5 in a week, so expecting him to do much to "attain" this power is probably out of the question.
2) The lore of the game so far supports that being turned by a stronger monster makes you a stronger Superhuman. The only one who objects to this is Nico and truthfully, not only she is the dumbest character in the game, but her examples don't really work. For example she talks about training being the reason she is the best, but she doesn't even need more power to shoot someone to space than she did at level 3. From there on, there's Syla who says that lesser spawn can be dangerous because their evolutions may cook up some overpowered ability.