size, heat dissipation, overstated capacity.

An NCC70 relies on simple relais to switch directions, and the single mosfet bank to control the power is mountend open on the heavely coppered PCB.

The TZ85's are Chinese build el cheapo speedo's for brushless motors, reprogrammed to act as a Hbridge speedo. All the power flows trough 1 chip with 6 mosfet banks baked in. Only 4 of those banks are used.

Reversing a Bosch 750 in a heavy from nominal draw means coming from 24V 40A to stall -24V 200A+ and back to 24V 40A inside milliseconds. This gets worst if the reversing is done when stalling or accelerating.

I think you see the potentials for magic smoke.

It's also the reason I wrote Big gear ratio and low top speed. This will lower the draw of amps.