I guess that may be an issue. Following @LiamN’s article on measuring belt tension, squaring and calibration, it was clear that any tension from 100 to 150Hz would be within an acceptable range. My guitar tuner is providing me with an accurate C3 note frequency which only equates to 130 Hz. This is well inside the recommendation and I have used this system for several years now and do not see any signs of bending the stepper motor shafts.
In truth, any misapplication of knowledge can damage the machinery and it is (IMO) up to us as users to ensure we are not doing damage to the machinery. I think there is sufficient knowledge available but as new users we have to gather it from all of the trusted sources and repositories. I agree with you and think that C3D should offer this kind of arrangement for tensioning belts. The costs are likely to outweigh the benefits of providing a robust tensioning system on low cost machinery, despite the critical importance of belt tensioning or tramming. It would significantly raise the cost of entry to new users and they would be unlikely to want that.