I recently received a large prismatic star for thieving. My P2P level is 91 thieving, yet I only got 447 bonus xp for it. In the past I would get the full members level bonus xp for stars.
I'm kinda bummed if this is intended. I enjoyed building up my bonus xp before I restarted my membership.
they changed that feature at least several years ago. this isn't anything new.
It was likely to prevent this exact scenario. go f2p, stockpile millions of XP in bxp (yes, yes, it'd take a lot of time) then spend 2 weeks of membership (doesn't matter if you pay directly or use a bond) and knock out the skill completely.