
Although your theory makes sense I dont necessarily think that is it. I think the Aquila hurt Uri's hand because he didnt want the past to repeat and Lamia to become duchess and die again.
And I think the only reason he acts cold to other people is not because he has an violent alter ego, but because he only shows his soft and vulnerable side to 2 people. His mother and Lamia.
Even though I do think he had to pay some sort of price, I dont necessarily Aquila is a different person or has an alter ego (in my opinion)

I really don’t think he the type to think that far and if he intended to protect Lamia, isn’t it better she’s a duchess instead of the knight which have less security. Plus the way he interacted with Uri showed indifference and that he actually hated Uri, it would be bad for him since he plan to marry Lamia. Right now it showing that he’s doing whatever it takes to earn Lamia and The Orphe family trust so why would he try to hurt Uri if he did return before that incident. I believe in the other theory for which this is the “badder (?)” timeline and that the Aquila before was the one who did that and not the one who time travel backward. Sorry I’m not good at explaining (〜 ̄△ ̄)〜
I wonder if there's multiple timelines and Aquila is living in a bad one where he hurts Uri and that's his consequence for resetting time to be with Lamia again...
Like maybe the first time he met Lamia, they had a good relationship where she became the duchess and Uri a knight and Aquila didn't harm Uri but when Lamia died, Aquila had to fulfill a criteria in order to reset time. So it's specifically that Aquila coming into this current timeline which is why he acts so oddly familiar with Lamia despite him harming her brother.
Maybe the Aquila in Uri's flashbacks is a different one or maybe the tradeoff was Aquila has to have a violent alter ego?
idk man but there's some wack time shit goin' on here and I really wanna know how it's gonna play out bc rn it's kinda cringe of Aquila to be acting all familiar with Lamia when she's like "...bro I have met you only TWICE WHOMST are you?!"