toTsFilePath and toResource both have the same comment:

 // Yarn v2+ hooks tsserver and sends `zipfile:` URIs for Vim. Keep as-is.
 // Example: zipfile:///foo/bar/baz.zip::path/to/module

however, toTsFilePath correctly returns the URL without doing anything, and toResource calls URI.parse on it, causing it to break and not be able to load the resource.