I recently purchased two Dremel Multipro 395 models (possibly run-out stock as I am fairly sure this model is no longer available in Australia) from a seller on Aliexpress. Both have excellent torque on start-up, straight out of the packet.
Possibly of more relevance to this discussion, from the same seller I purchased some spare brushes. As they are in unmarked bags I can't guarantee they are genuine Dremel, but these brushes are plain ended i.e.flat – no ground-in shape at all. If this is the way machines are currently being supplied it would explain why a run-in period is necessary.
Incidentally, I am still using my original Dremel (grey coloured case and bronze bearings) purchased over thirty years ago. It has no speed control and makes lots of noise (always has done) but still cuts its way through all sorts of materials, including stainless steel when treated kindly.
Pero