Nice catch ! Could be the motor manufacturer of the Whimsifoil Plume efoil using a “Patented” waterproof outrunner motor.
They charge an extra 40usd for the waterproofing as per https://saite-motor.en.alibaba.com/minisiteentrance.html
The 63100 is 4500W so 50% more powerful than the 6374 and should cost 140usd waterproofed.
Why do they shorten the shaft only when they waterproof an outrunner motor ?
Credit @pablo_foil: DIY electric foil assist. Steps+pictures+cad files