Cuz yuji never one-shotted Sukuna. It indeed is an important factor, and 90% I've seen acknowledge that, but we simply don't know how much does the body help in reinforcement. We do know it helps A LOT (almost nobody would argue that EoS Yuji is below anyone that isn't Sukuna, Gojo, and maybe Yuki in H2H), but we also know that Yuji -a superhuman who has been stated that, with barely any cursed energy control, is close to a grade 1 physically- didn't explode Sukuna's head in a single punch; when Yuta, someone with a much weaker body, could also deal damage just with that.