@mhmm.. gojo uses his specific handsign because it utilises a different part of his brain (i think the occipital lobe if i remember right?) when casting his domain, think of it as a different pathway for cursed energy to flow into.
We know from earlier chapters that sukunas brain was damaged due to experiencing infinite void from his battle with gojo, but the same part gojo utilises wasnt as damaged, so sukuna used a binding vow to redirect his cursed energy into the same part of the brain as gojo does which is why the hand sign is different.
'Yaoi is goated, I personally find it more romantic than straight stuff.'
I say 'what the sme***' a lot.
I say 'what the sme***' a lot.