So how do you stop then if the batteries are (close to) fully charged? You'd need to shunt that power into a big resistive load, and then dump that heat.
Just have the battery stop charging and report 100% full when it’s only 98% (or whatever) so there is enough capacity for some solid emergency stops in the first few minutes of driving.
Even if you have to resort to the resistor, who cares? It’s not like this is a common scenario
Regenerative braking also loses a lot of its stopping power at slow speeds. Going from "slowly rolling forward" to "full stopped" takes a lot longer than the instantaneous it is with friction brakes.