Ultra Instinct appears strongly to be a very bastardized version of the concept of mushin, that is, of moving without thought. It's not precognition; it's simply removing conscious thought from your combat routine and letting trained instincts take over completely. The reason doing this is gainful is because thinking about something delays you from doing it. Learning to trust your instincts and sustain this state is a very long and difficult process. It looks like precognition because it lets your reaction times spike so high, but in reality it is at it's simplest just weaponizing and streamlining the flinch reflex.
Also, its depiction via ultra instinct in Super makes me absolutely furious for reasons which aren't gainful to discuss here, but that's ultimately secondary to the point of: no, this wasn't UI.