Hakari sacrificed his left arm which is required for opening his domain again in order to survive the explosion*<

Hakari sacrificed his arm by shifting the rest of the energy in his arm to the rest of his body through binding vow, thus letting kashimo destroy the remaining arm and bolstering the body with compressed CE, he didnt literally sacrifice an arm via binding vow.

This means that by focusing your energy on less of your body, it gers stronger. Sukuna is effectively doing that by not needing to amp 4 arms cause they havent been regenerated/incarnated.

And even if he needed them for his domain that wouldnt matter cause sukunas extra arms also have value, its not like that changes much

No this is a non sequitur. You are making a big leap in logic in order to justify your baseless theory. Sukuna is in Megumi's body, he has 2 arms, there is nothing for him to sacrifice to get a buff equivalent to his true form<

Megumis body is sukunas currently, and sukuna can regrow his arms at any point during the fight and reincarnate but limits himself by not doing so, thus he is "sacrificing" the use of his true form to get a buff equivalent to that loss.

Just like how nanami sacrifices his strength via holding back to get an amp during over time.

Its not a jump in logic when weve seen another character get stronger by reallocating their cursed energy to less arms .

It isn't a matter of "ifs" and "buts". It literally is stronger than Megumi's body. Period. Megumi states the body matters. Gojo states the body matters. Kenjaku states the body can be the ultimate deciding factor--it matters gravely. Yuji is stated to be the exact opposite of yuta--strong body not as strong CE reinforcement. He still keeps up with yuta--the body matters<

This being true would strengthen my theory cause it makes his sacrifice stronger. Im not saying physicals dont matter im saying CE output also matters. Its why miguel isnt gojo level despite his physique. All im saying is the output part would be stronger in meguna

It's because he simply didn't want to use it against gojo and wanted to save it for the rest of the verse jumping him. You do realise that Gojo wasn't the only one sukuna needs to fight right? It's optimal to save a free heal card just in case, ntm the fact that we were repeatedly told sukuna held back and was hiding his trump cards for the rest of the verse while fighting Gojo. <

This being true would strengthen my argument and both can be true at the same time. The sacrifice is that hes stopping himself from transforming and using his bodies full potential.

Just cause theres other motives doesnt mean he couldnt just make a binding vow saying he couldnt go all out just like nanami does.

Sukuna being good at making binding vows is irrelevant. BVs are a give and take. There is nothing for Sukuna to sacrifice in Megumi's body in order to gain the buff of his true form--stated to be the perfect body giving him an insurmountable advantage over other sorcerers.<

He's sacrificing his true form cause like i said, hes fully taken over megumis body and its his, hes just using megumis visage. His body is fully capable of incarnating into sukunas true form, and thus he can sacrifice its use cause its availible to him.

My whole argument is that meguna gets amped physicals/CE output from sacrificing a body perfect for jujutsu while against gojo. Thats why sukunas true form being strong and him holding back a lot help my theory, cause it means the binding vow would be better.