I think in pretty much every state releasing the refrigerant 'requires' a license (if it's not a DIY model).

And in my state, I copy pasted what was required for a 'residential' HVAC license (idk if you meant commercial HVAC or just making money on installs).

Not Montana apparently. They don't even have an HVAC contractor license anymore that I can find.

Exception rather than the rule

100%.