> There might be some merit to a claim that Google Drive isn't a medium customarily used for software distribution these days

I suppose forcing a means to share the source code could have been too restrictive, but the GPL only speaks about the shape of the source code itself (it should be "the preferred form of the work for making modifications to it"), not how it is shared, so indeed, not a violation of the letter of the GPL I think.

It's like what we had in France and the Hadopi, which requested ISPs to share the IP addresses of people torrenting a defined set of files. One of them sent them printed on paper... (But the malicious compliance was cool in this case).