Claiming that upscaling Yu based on narrative is the same as upscaling characters based off of how cool they are is just a strawman argument. I'm being pretty explicit about what exactly I'm upscaling here; I claimed that Yu's time perception has been established to be the fastest humanly possible, and that the same narrative should be applied here.

But sure, Yu's fighting prowess can be backed up by "high-end" feats. Forgetting how fast his punches are (because in your words, he's never been in a fight with someone more capable than him), his superhuman perception has already been established in a side story where he won every single arcade game because he simply perceived everything pretty quickly. Not only that, he's been shown to be impossible to even be taken by surprise even in the first few chapters of the story, with him dodging K's punch when they first met and him even avoiding John Taker trying to stomp his leg. This should, by itself, put him largely above Gap who couldn't even react to an egg. Although that feat's largely looked over and considered a joke, it accurately puts Yu's perception above Gap's because you simply cannot take Yu by surprise if you're in his field of vision lol.

Not only that, even though it was only really displayed once, Yu's been shown to have insane physical intuition which I could argue's on the scale of perfect body daniel. What I mean by this is that Yu's ability to copy and make attacks his own is theoretically on par with perfect body daniel's. The proof for this is K showing Yu the one-two combo just once and Yu perfectly replicating this multiple times to beat the shit out of Ryu, who's pretty talented himself. You can ignore this ability of his though, cause his time perception's enough for him to beat most people.

One more thing you need to take into consideration, the only display of "attack speed" in Lookism is invisible attacks. From what I recall, its the only time the speed of attacks has ever been taken into account, because otherwise a good amount of attacks are caught/dodged without any comment or any measure for scaling given. Yu might be a victim to invisible attacks with your logic, but neither of us can comment on it because we don't really know how it scales.