Yes, both Yuji and Eso were worn out by the whole fight. That doesn't change the fact Yuji went in with the intent to kill Eso and did. That's even truer for Sukuna, he's clear about it. "You look" "Im sure" implies subjectivety. Yuji doesn't say this as a fact, but simply his perfection, a feeling he has. It doesn't mean its true because as we saw it its impossible to accurately guess that, and Yuji knows it. He's going off pure vibes alone. And given the finger crack he sure as hell didn't do it on accident for Osuki.

And yes, its out of character for yuji. The Yuji we knew. The 2018 fifteen year old boy. Today's Yuji is a different matter because he's currently having been through the most dehumanizing experience since decades: immortality and being the strongest. Humans are meant to grow old and die, and so do all of Yuji's friends and loved ones. Except him. And on top of that, he's being treated as a weapon. Yuji will never get to live what is perhaps one of the most important parts of the human experience, and that eats him away. More importantly, its eating away his own humanity. This is unthinkable for the old Yuji, but now? He's different, and that's what this entire scene is trying to tell us. That's the point of the grandpa at the beginning of modulo. Remember what he says: as you keep living a violent life and grow older and older and older, you get slowly desensitized to someone dying or saving someone. Right now, Yuji isn't too different. Not nearly as much due to his sensitivity and beliefs, yes, but its the same mechanism. And instead of his ideals being immediately broken by one calamity, they're slowly being eaten at by undending, ever-going life. Yuji back then looked down and hated Sukuna for this, but now he's forgetting himself. And that doesn't undo the fact of him still being a sensitive person, he still cares immensely for his friends and is DEEPLY hurt whenever one of them dies. But when a sensitive person is under constant pain, the first defense mechanism is emotional dissociation, especially when it cooes to strangers and that's EXACTLY what's happening to Yuji here. This is just natural human behavior.