[2019] "you’ll receive greater overall rewards the higher the Division you qualify for"

Your division does not affect your end of championship rewards. It will however affect your league promotion rewards (i.e., you will get more rewards when promoting from Carbonite to Bronzium in Division 11 than in Division 1).

As others have mentioned, these rewards are for the Exhibition and are not final.

Check out CG_Cyanides post about Exhibition Rewards for more details: https://forums.galaxy-of-heroes.starwars.ea.com/discussion/206819/exhibition-gac-rewards-and-beyond#latest