> Seems like Amazon can just force third-party vendors to reveal their full legal identity to the customer then?

Minimizing the prominence of seller identity and maximizing that of the Amazon brand has been a key Amazon business strategy; they very much want sellers not to matter.

I suspect, though, that even were that problem cured, their commingling practice would leave them liable unless they also allowed buyers access to the identity of and the ability to reject transactions based on the original product source (which may not be the seller, due to commingling) with FBA products.