Is someone with Whitebeards shadow put in them? He has cuts stitched like all of Moriah's Zombies. Moreover, the side of the face stitched just happens to be the one which Akainu fucked over with Lava. What happens if that damage was transferred to the shadow and affected the host body? Mind = blown.
Don't think it has to do with shadows more of with his "mother" who made him think he is WB's kid,wouldn't be surprised at all if she brain washed him and did everything for money tbh. Then again we don't know if it's some kind of awakening for Moriah to take dead shadows in the blink second before people die :angel but I doubt so.
Well if you think about it, WB was standing when he died it isn't far fetched to think that moriah came and cut his shadow, I mean dead bodies do technically have shadows.
Weeble doesn't seem "all there". A soul fragment or merging the shadow with another soul or some shit whilst far fetched, would work here.