@Lyth The lower level person doesn’t get any extra rewards. They see the higher level players cards as a lower level (as if the higher level player were playing in their arena). The higher level player likewise sees the lower level player as if the lower level player was playing in the higher level arena, with their cards boosted up partially, as needed to make the match competitive.
The net impact is higher level players don’t have to wait as long for a match. It’s purely a good thing for high-level players.
Arenas help matchmaking by only exposing players to higher level opposing cards if they opt into it. This puts more control into players hands. When players opt into it, they will also get higher rewards, so its worth fighting for (imo). Arenas don’t help liquidity – that is, there are no more high level players now than there were before. So, for now, we still need to make these special matches in order to help high level players like you. If we didn’t do this for you, you’d have to wait in queue (much) longer on average and your long-term win rate likely wouldn’t change – a purely worse experience.