isMeters variable name(s)
There are two parameters in the proposed IDL that have inMeters in their name: measuredWidthInMeters and widthInMeters.
As XR units are already in meters, and other APIs don't have this name definitions, is that needed in this API?
I'm open to suggestions, but I think that an attribute named width that's provided alongside a bitmap image is too easy to misinterpret as a pixel width. It's not immediately clear from context that this is intended to be a real-world dimension.
Yep, you are right. Apart from realWorldWidth or worldWidth that corresponds with worldInformation from plane detection (which is also not ideal) I don't have any better suggestion.