Not at all. Sorry if I gave that impression. I wasn't familiar with the R12a until I read about it here. Started to look around and found the quote I posted.
I think a lot of people (lacking knowledge and experience) will put just about anything in their system, leaking or not, if they think it's gonna give 'em some cool air on a hot day.

Thanks to advertising and marketing, all ya gotta do is.......(buy this can, with the little hose and cool little gauge with green and red zones, squeeze the trigger and "off ya go").

As I mentioned, I was only cautioning people. AC is pretty serious stuff. I commend you on your knowledge. You're the first person I've ever seen post here that exhibited a thorough understanding of gasses, vapor and pressures. Also NEVER heard anyone address the issue of the refrigerant blends changing their composition as they leak out and pressures fall, thereby changing the entire property of the gas.

Yes, it is a "paradox". I can't speak for every car ever designed, but I think MB kinda messed up by making their evaporators so ridiculously difficult to R&R. Hard to find fault with these old Benz's, but that IMHO is definitely one.