There are stacks of subsystems that can be tested quickly, janky, yet safely. Safety is always paramount, but a relative term. Safe for an end user, and safe for a prototype engineering test need not be comparable. Similar safety, for sure, similar longevity, ease of use etc., potentially very different.

For tests on prototype subsystems like a cooling system? Totally fair game

Live full production systems? Usually no one will be willing to risk the OSHA or ISO violations where critical failure affects safety. Or, if they do, that company won't last long