I'm not an expert, but a high power device safe load means that it won't place a lot of the load on itself. when it places the load on itself it gets really hot, so hot that parts may melt, and things that were supposed to be insulated may now be conductive.
Doing high voltage electronics without a license is a crime in a lot of places. I'm pretty sure a person with the right specialty can add a load so you won't need to hack up the firmware to violate its safe operating ranges.
If someone told me this in person I'd consider contacting authorities over their negligent behaviour. The manufacturer was willing to lose business for a safety matter even though allowing the firmware hacks would be really easy.