To my knowledge, the PoE standard requires a Switch to be capable of detecting whether a connected device is PoE capable before delivering the full power via PoE. Why is there still often a warning, non-PoE Equipment might suffer damage if connected? This seems kind of contradictory to me?
There are some poorly designed or constructed devices. We experienced this with some devices that had pins shorted in a way that requested PoE from the switch, but the devices could not handle PoE, and they blew up when connected to a PoE switch interface. This was a design defect in the devices, and we needed to disable PoE on the switch interfaces where those devices were connected.