Hasn't this largely been fixed? I remember reading about how the tor browser would fake its window size to be from a predefined set that's somewhat near your current window size
Yeah, it does a pretty good job at letterboxing. It doesn't make Tor perfect, even if you wipe your identity, if you have a less common predefined size and go back to the same URL, they can probably track you as the same user, especially if combined with things like canvas fingerprinting, but if you set Tor to the safest setting, which disables JavaScript, you are completely safe.