I think the idea that the Suzhou Bafang fitted to the Mistral has brushes arose from postings to the effect that it is difficult to pedal without power, some users using the word "drag", others "cogging". I was concerned about this prior to purchase but went ahead anyway. I cannot say there is much evidence of cogging, but possibly there is some drag. However, I think this arises more from the weight of the bike, rather than the brushes, if there are any. And if the battery is removed from the unpowered bike the weight is reduced by 4.6 kgs, making pedalling, albeit in lower gears, easier.
The front wheel Suzhou Bafang fitted to my Speed TR is sold by Alien Bikes as "brushless" and I have not found much difference between it and the Mistral motor when power is unavailable.
However, I am not much of an authority on all of this as I endeavour never to run out of power!