The files in question are flacs. Adding cover art increases file size. Removing cover art doesn't decrease it, then what's the point of removing?
I had to install Mp3Tag because i couldn't make my foobar2k delete cover art at all. That alone shows my capabilities to understand things, so please explain to me as to an idiot, though some things i've already learned from this forum, like, tags are held in a container which reserves some fixed space at the beginning of the file, and if a too large picture is being embedded, more space will be taken… and never given back? At the moment i know one way to shrink files to their state before adding pictures: it's re-encoding them > WAV > back. But i could bet there's something simpler.