IMO they should whitelist a couple common resolutions. 1920x1080, for example, is extremely common and probably doesn't need to be letterboxed to avoid fingerprinting.
Nah sometimes you need to resize manually read a webpage. Gotta keep usability at least a little bit. Letterboxing I think is a good compromise
I don't think Ajedi32 disagrees with you. I think Ajedi32 is saying that in addition to the all the resolutions that are a multiple of 200x100, a few more resolutions should be allowed, such as 1920x1080.