The problem is that the "ButtonParagraph-Default.xnb" file *doesn't* get put in a folder, because of a quirk in how the zip is produced. On filesystems that don't use `\` as the folder deliniator (so everything but windows), it creates a file at the root folder *named* "Content\GeoBit.UI\themes\editor\styles\ButtonParagraph-Default.xnb", which looks very silly and also doesn't really work right :P
If I had to guess, it's the native windows 11 file explorer you used to create the zip file that is doing it badly, although unfortunately it's not an issue you could really replicate on windows!