Will the FB see P, though?

Looking at AFKL flights where you are booked in J but sit in Y if there is no business cabin. Flight shows J class, miles are credited...as Y. You get credit for the cabin flown, with AFKL at least. We don't really know how deep the integration between Etihad and FB is, although I'd probably expect it to credit at the listed P numbers. But it doesn't have to.