OK, just did some research. Seems like Y1234R is the chosen solution for cars because - while R-134a dealt with the ozone depletion angle - it still has a high global warming potential. (The stated issue with R-410a) So, they came up with 1234 to address that. Only problem is it is flammable, though stated to be only slightly flammable. (This is the problem with R-32, the gas to replace R-410a). How can they put a pressurized flammable gas under the hood of todays hot cars? And what about crashes? They did summersaults trying to aleviate fears of it's flammability. That's my issue with R-32. I've seen house fire videos where the condensing unit gets enveloped in flames, and eventually pops. You've got close-in explosive damage and probably toxic by-products. But you don't have additional flammability concerns. I'm thinking though they modify the flammability codes and find a way to slip it on in.
Oh, and 1234 is 10X the cost of 134a. I expect R32 to be likewise golden compared to 410a.