It’s fine
Use whatever braking strength you need for your ride to perform how you need it to. Unless you’re towing a car down a hill, your cells probably will be fine.
Though I believe there is a phenomenon where if the state of charge is in the upper percent or so, higher charge rates can be significantly worse. But this is just an edge case, IMHO getting to a speed high enough for that to matter would likely bring your SOC down to level where that’s no longer mattering.
But aside from that, -20A battery current is a lot of braking, if you’re talking about -20A per motor battery current with at least 2 motors, that is a very significant amount of high-speed brake already.