The RAF bonus only lasts for 90 days, so perhaps that's the reason why.

If you had a high level character on Account 1...and got account 2 to refer account 3...then I think you'd be fine. Accounts 2 and 3 would get the RAF XP boost and as 1 isn't linked to either of them, then that shouldn't nerf the XP. I'm not 100% on that though.