This stuff has always been how factories work
a lot of them make similar things for different companies and just change the quality depending on the customer
When I used to work for Littlewoods I was talking to a guy in the Chain STore section one time when I was at a warehouse for a few days and had to stay in a hotel.
He worked in the quality control section and visited the factories than made the clothes. An Article had recently appeared in a paper saying that shirts (or whatever) made for Matalan were just the same as those made for Littlewoods
I was wearing a shirt from Littlewoods and he showed me the stitching and seams and stuff that we specified and how Matalan specified them differently which affected the quality - and the price paid to the factory
But the end customer would never notice the different - until it fell apart in2 years rather than 3 years
The same applies to ebike - the factory may make similar bike for several companies
but the cheapo ones will not be made the same as the expensive ones
(unless they can get away with it and the company doesn;t notice!!!)