The device that can be damaged is a DJ controller with haptic feedback. So it has motors in it, and some kind of audio outputs. If the audio levels get turned to maximum or the motors get sent invalid commands, it could cause the device to damage itself. I’d call it a firmware problem if the motors can be commanded to move too fast, but anyway it may be reason for them to warn their customers. The editorialized hacker news headline makes it look like Big Sur is to blame, but it could easily be written as “Native Instruments Hardware does not fully support Big Sur and could be damaged if run on Big Sur.”