Yes, if you release propane into an enclosed space like a mechanical room and then introduce a spark, it could cause an explosion.

The explosion risk (in a commercial setting) is mitigated by having gas detection sensors and an exhaust fan that runs when the gas detection alarm trips along with horn/strobes at any entrance to the mechanical room and inside the mechanical room.

In a residential setting, I’d only feel safe if the condenser (outdoor unit) used propane with a liquid to liquid heat exchanger and separate glycol loop that runs inside to the air handler coil.

The shareholder value is being able to continue to develop and sell additional generations of refrigerants.

Flammable I guess