Yeah this is ridiculous. Neither project has copyright notices in preamble comments at the top of files, or an AUTHORS.txt, or any other kind of copyright notice. Therefore there is no copyright notice to preserve as stipulated by the AGPL. While it's best practice to preserve Git authorship by using properly formatted patch files (like he did for the first commit), this isn't technically required.
It's also debatable whether the stylesheets copied here are even substantial enough works to qualify for copyright to begin with, but that's another discussion.
The Piefed author should merge all that code right back in, but use git format-patch for both commits so Git authorship is preserved. If the fork fellas don't like that, they should shutter their fork and go fork a project with a more permissive license that allows them to relicense to closed source.
edit: I imagine the only reason the Pylova fork authors even cared or noticed is that the stylesheet commit showed up as a merge conflict when they were merging in upstream code -- something that would not have happened if the code was merged in using a proper patch file. My guess is that there was a game of broken telephone at play here when the Piefed author heard about this from some third party.