There is something else that hit me last night which may explain the devs motivation to make the tweaks they have but kept the xp leaderboard.
So in Rivals mode they have made it so rewind dirties a lap as does contact, so wallriding is out (for rivals mode).
Well what about online racing? What did the devs do to improve that?
Well lets double the clean racing xp granted to try and provide incentive to race clean and off the walls.
So I believe they have kept the xp leaderboard and doubled the clean racing xp in an effort to clean up the racing. (refer to JONK1969 post in the thread I link earlier to see him say they had doubled clean racing XP.