Do you think it's easy to confuse Quasi-identical types? For me, it's much easier to confuse Benefit partners.

It's true that quasi-identicals have two shared 4D functions, but Benefit partners have a shared 4D function and some shared quadra values. I don't think I'm alone—IMO people confuse EIE and ILE more than EIE / IEE or ILE / LIE.