GPLv3 explicitly says that you can link to the source being available elsewhere ("may be on a different server (operated by you or a third party)"), but if that server goes down, you have to come up with a new link. And of course, that only works if you're using the package unmodified; the source you link to has to be the source you compiled.

So it's not as if the FSF isn't trying to make things reasonable.