What was a key design change for hfc-134a a/c system versus cfc-12 a/c systems?

I believe the answer is: quick couple service fitting and that design reduce venting and mixing of refrigerants during service.

hfc-134a has a better process of refrigerants venting and mixing compared to cfc-12 a/c system. This reduce the toxicity level of air conditioner which make it possible for the Air conditioner to be installed in small/cramped space such as cars

Corruption i think