This breaks in the case that the endpoint actually does use the referer for something. I have actually encountered plenty of cases where a site will use the referer internally, i.e. on the same origin, to check something.
Yeah that's fair, but I haven't really noticed it for myself, but then again, I disable javascript by default and have compiled a lot of other stuff into the netwerk module that probably breaks sites even more to the degree if its noticeable, i just don't use the site.