I wouldn't know if Ilford makes a third party product and sell them under completely different brand names. I do recall Simon saying this isn't the case. I really doubt it is worth anyone's trouble to make a special blend just so they can produce third party papers.

Adorama paper looks and behaves so differently from any of commonly available Ilford papers. I just use them because I like how it looks and behaves. (and it's inexpensive) In particular, FB Matte is great. Tones well and the surface is more like semi-matte than matte. I'm curious who makes it but I don't think anyone who really know will be talking....