My take on it is that in my own work I really like transparency effects but it is always a chore to tune up the foregrounds, backgrounds and alpha blending to keep everything legible. If you control all the content it is one thing, but for a general-purpose OS where the content is supplied by the user and applications you have to dial the intensity way back.
When I first saw the prototype images I thought they were really cool and it was a bold idea though people on this site were complaining about it already for the predictable reasons.
When it came out I was thinking that they dealt with the legibility of the content by dialing down the legibility of the design -- like it looks like "anti-anti-aliasing" more than it looks like "bold transparent vision"
One reason I don't think I read it as "refraction" is that one of my tells for refraction is chromatic aberration and without that it doesn't seem real to me. I think it would triple the texture lookup rate (at least) and make content legibility worse and I think you would see a lot of people say it is was an ugly gimmick.
Technically, I’m awed by it. Very cool visually. It’s just when you go to use it that it all falls apart. As you say, they can’t control the content it’s flying over, and thus sometimes it does bad things. But also they rearranged navigation and some other things. I try to keep from rejecting new things just because they are new, but there were some serious usability gaffes in both iOS and iPadOS. Interestingly, macOS doesn’t have the same issues and I’m actually somewhat ambivalent about it.