A few things here:
1) We saw Jogo and Hanami bypass Infinity using domain amplification. Sukuna should be physically much more powerful than those two, meaning he should be able to damage 👖 with just his physical attacks alone.
2) Fake Geto/Noritoshi Kamo literally said that Sukuna was a contingency if the Prison Realm didn't work. How does this not directly imply Sukuna > 👖??
3) Sukuna's techniques seem relatively unknown. Even Jogo, who likely had full access to historical information, had no idea what was going on when Sukuna summoned the blue flames. 👖 said he would win, but he also probably doesn't know what Sukuna's packing.
4) The description of dismantle and cleave. Cleave adjusts itself to the power of its target. A lot of people are taking it to mean it adjusts to physical power, but what if it adjusts to all defenses?
5) Sukuna's domain is MUCH larger, and thanks to the binding conditions I think Sukluna would outright win if they decided to lay out their domains.
6) From a meta-narrative perspective, it makes no sense for 👖 to just beat Sukuna after he reaches full power.
7) 👖 can't even destroy Sukuna's fingers.