Wokistan said:
I think it's more just a showing of Goku's ridiculous stamina, and that UI just kinda helps him focus to push through the damage he suffered. You'll notice how in the end it all kinda catches up to him when he can't just ignore being badly beaten anymore and collapses right before he could finish off joren.
That was simply the
time limit of the Ultra Instinct ending, and as far as we know had nothing actually to do with the injuries he had sustained (i.e. we have no evidence that the time limit would have been any longer even if he had been far less injured upon activating U.I., and with this wiki we are only able to go by evidence canonically presented in a series, not speculation).
A lot of people in the DB fandom, especially those like me who are ultra-geeky superfans (lol), are of the opinion that that was NOT just a showing of ridiculous stamina; Goku has had showings of such before, yeah, but what he did with U.I. seemed fundamentally different. Whenever he would enter U.I. Omen, and then later full U.I., he seemed to not merely be "pushing through" his injuries, but to be actually completely and totally unaffected by them. While Goku has fought while seriously injured in the past, it was always the case that he at least seemed AFFECTED by those injuries; that is, until Ultra Instinct came along.
It would seem that activating any version of U.I. causes some kind of
temporary Regenerationn of injuries lasting as long as the U.I. state holds out, and that as soon as the state's time limit ends, all those injuries immediately return and stack on top of any damage taken while using U.I. or from the after-effects of U.I.
Yes, Saiyans do heal faster and better (i.e. wounds that would leave a scar on a human leave no scar on a saiyan after healing) than humans, but not THAT much faster; i.e., their regen is not normally fast enough to actually be combat-applicable, and is only good for helping them recover when they have hours or days to do so. That's one of the main reasons why Buu was able to give the Saiyans so much trouble in the final arc of DBZ; he had combat-applicable regen, but they didn't.
But on the other hand, when using Super Saiyan God (at least the version granted by the Ritual), it would seem that a Saiyan gains both a higher level of Regenerationn, as well as a Regenerationn-speed making the regen combat-applicable, as seen when Goku regenerated a hole in his torso during his fight with "80% Power" (lmao, yeah right dude) Beerus. So U.I. regenerating injuries as well really doesn't seem far-fetched.