- #34
have, but the stitches may simply be there because their bodies needed fixing and putting a device in their brain to control them was a necessity if he was gonna use them. It's doesn't mean that he managed to upgrade their power too though.
If you go back to their fights back in the Fake Karakura town arc, you'll realize that the places they have stitches on now doesn't correspond with the areas of their body they were injured in. Thus the supposition that Mayuri has done much more with them.