It is about weather/rain proofness , I know.
YOU see it also depends on how the BIONX drive is installed to reduce water penetration to minimum,
BIONX drive cannot be responsible if the the dealer foolishly for example run the power wires into the motor without rain loop. I mean wires MUST first run down below axle and up into the motor - it is called loop.
In general all power wires, communication wires, etc. must enter from the BOTTOM of device, never from the top. No matter what gaskets, silicone you use water will eventually enter, do not make wires guide for water to enter.
On my TIOBA Edvin BIONX I had to reroute /loop it/ power and comm wires into the motor, because factory run the wires straight from top into motor - bad, bad.
Never try to beat law of gravity.