In contemplating refrigerants, it's helpful to understand that it has almost nothing to do with refrigerants per se, but rather a cosmic battle between patent holders, politicians, big business, auto manufacturers, bureaucrats, militant environmentalists and regulators.
Absent from this list are refrigeration physics, DIYers, auto owners and science.
Once you understand the larger environment, it makes complete sense that perfectly serviceable refrigerants like good old propane and close relatives are shunned - there's just no money there, it can't be regulated and taxed, and the shops would lose valuable business.
Your chances of getting caught running an "unauthorized" refrigerant are close to zero as long as you don't trash a shops stash of recovered refrigerants or brag to an EPA life form.
A good amount of the information out there comes from "interested sources". Just like the "fake news" promulgated by those with a vested political interest there is a lot of "fake" science and information surrounding refrigerants and getting solid information takes a lot of work. "Political Science" isn't just about traditional politics anymore.
Not suggesting anyone break any laws or believe anything in particular....just commenting on current reality.
....and even the claims of the alternative refrigerant purveyors must be taken with the reality that they too have a vested interest
Good luck!