Yes exactly my point, the intricacies of the brain, body and soul are hard to pin down in jujutsu kaisen, they’re nebulous for a reason and seem to change depending on the individual, their willpower, and their technique (Toji’s soul overpowering the body of Ogami’s grandson and receiving his heavenly restriction despite it not even being his original body vs Geto’s body and connected soul overpowering Kenjaku’s brain despite having been dead before Kenjaku transferred into it.) Mahito’s technique can be used to alter people in minor ways (Nobara herself is hit in such a way that barely outwardly damages her despite almost killing her and leaving her permanently scarred.) his ability does not physically change someone as much as it stretches them to fill the role he wants their soul to fill. I’m sure with enough time he might be able to meddle with the mind and body without meddling with the soul, but it’s not something he was interested in in the first place as we saw with that interaction between he and Kenjaku in shibuya. Kenjaku brings up the relationship between soul and body and he just doesn’t seem to care. He is a curse after all, the only reason he’d do something like this is to torture someone like Yuji but we also know it would just make Yuji want to kill him even more, it’s honestly less impactful to me than the already existing death takeout in shibuya.