[tajen]

As far as I understand, whether it is "sold by Amazon" or by a third party, they put the same products with the same ID in the same bins. Traceability is thus broken, and whichever origin you've selected, they take it from the same bin.

Now I take the question the other way: Amazon's UI confuses the user about the third party products, which is the opposite of giving clear information about genuineness and traceability. The day it matters to them, they'll proudly say "Not a Third Party".