I asked this very question to the GA on my recent LAX to SEA flight....she said they board back to front for Y after calling F and the Y+ seats.

What seemed odd to me is I had 2 row behind the exit seats and was in boarding group C on the return flight was in row 5 and my boarding group dropped to F.

My only complaint VIRGIN WHY DON'T YOU BOARD YOUR FOUNDING MEMBERS RIGHT AFTER F AND Y+ ???? Virgin Elevate Founders - how many are there and how many would like this?