In my understanding, Facebook and Google have centralized interviewing, whereas at Apple each team did its own hiring (my team of ~40 had their own recruiter, did all their own interviews, etc.). Amazon I believe is similar to Apple but the teams are larger? When I interviewed there it was all for the ads org, and there weren't people from other parts of Amazon.

I actually had quite the opposite experience, Apple absolutely grilled me at the spot for its interview, even though I did pass it, but I didn't take their offer.