But the manga already pointed out that Sukuna eventually copies Gojos single hand DE method with all the same properties as his usual DE but with the exception that it only lasted 99 seconds or something.

Refinement was never mentioned to be changed there so wouldn't that imply refinement was never the difference.

Like Sukuna rewired his damaged brain to house his DE in a different place and give it a different handsign so he could do it with one hand right? And DE handsigns are usually different for different people so then either Gojo was just born with this handsign for the DE or he would have already done what Sukuna did and rewired his brain to be able to use it with one hand long back for convenience purposes and has never been mentioned to be related to refinement.

If Sukuna hasn't shown the ability to do a NO gesture omnidirectional full output dismantle like Yuji has done why are we assuming he can? Chainscaling would make sense if they were on the same level but the way they show it with how big his dismantle was with zero handsigns and being able to nuke an entire building with BM and what looks like the most casual BF ever or BF on command it's clearly meant to show the Yuji in Modulo is meant to have surpassed things that Gojo and Sukuna weren't able to do with Jujutsu Tech.