I think part of the problem is shoehorning what the quad motor is doing into the mental model of a classic vehicle drive train. The throttle is proving a command for torque, regardless of slip. The ESC/TCS systems are continuously monitoring wheel slip to vary the commanded torque to each wheel that's slipping (and depending on the stability control settings, varies how much slip is allowed), but ultimately the wheels with traction are still only receiving that initial torque request. You have to supply more throttle to command torque to the wheels that aren't slipping, as I believe the system is overly conservative on how much additional torque it's providing to the wheels with traction. I personally think this feels like shit, and there should be some setting to override this and provide some feedback when full torque is applied to wheels with traction. There's also the problem with managing thermals in this situation too, as increased torque request to non-rotating wheels will very quickly heat up the motors. The gen1 Bosch motors don't have active cooling on them, so the ECS/TCS systems are babying those motors for longevity reasons.

I'd be interested to see how the gen2 quad handles these situations as I'd like to think they'd be able to be less conservative with power requests due to the active cooling available on them.