It's definitely not as standardized as it could be, but it's not far off. The UST thing with Mavic was more marketing than anything. So now everyone else has to label their own standard to avoid copyright or some such, but essentially they are all pretty much the same.
More realistically, though, I don't know why people seem against running sealant. That's a huge benefit of tubeless. This whole thread was started because you were excited about how well it held. But some people insist that because it's "supposed" to be air tight, you shouldn't have to run sealant. I don't get that. Sealant is awesome. Why not put it in? And when you do, all this issue of what tire works best with which rims, etc. really means nothing.
Compared to the heavy duty bead of a car rim plus the tire and the standardization in that industry, it's not hard to imagine that a substantially smaller bead on a much smaller piece of real estate is not going to always be perfectly air tight.