Thanks, Irishguy. So... the plot thickens..

I called Etihad guest to select seats. They told me the ticket wouldn't earn EY miles unless I filed a request for a credit afterwards.

Why? Because A3 and EY don't have a relationship re: FF. The A3 ticketing is A3's answer to the lack of coverage beyond Europe.

This seems like a hassle. Essentially, I'm paying less for the ticket through Aegean to forgo all miles except possibly EY, if I submit post-flight and they accept.

Funny.