Yes, yes it doesJust because Shirou was able to to exchange blows with Kuzuki doesn't mean their strength is similar, and the way he did it was very much not fine.

His 30 strike exchange from the start (let alone greater development that doesn’t dampen his senses in the moment) should have ended with one if Kuzuki was even twice his superior, and I’m exaggerating a gulf. He should have folded Shirou’s attempt with far less force than twice over
No, the function of weight classes IRL should tell you just how bullshit that idea is when pithy differences in strength determine significant differences in outcomeArcher can have 10 times the strength of Shirou without having nearly that much of a difference in strength with Kuzuki.
Stick to simple lore, actual functions of comparison are beyond you

I was never even more than 1.3-1.4 times the strength of a potential step sibling, he could do fuck all to me even in a friendly spar while he tried his hardest.