This is to make sure we can handle new gauge types on the Curve platform. Stashes control extra rewards (SNX, BOR, PNT, LDO, etc) by claiming them from the curve gauge and transferring them to Convex reward contracts.
Before Curve v3 gauges, if two gauges have the same extra reward (currently stkAave) it is impossible to tell exactly how much each pool is entitled to. Thus if two pools share the same reward, these rewards are pushed to an arbitrator vault to later use off chain logs and redistribute to the appropriate pools.
Change platform fees allocated to stakers within hard-coded ranges.