Sounds about right to me... but it's hard to decouple things so neatly. It wouldn't really be possible to create an SVNHub that worked as well as github.
wrt SVNHub, well, probably you're right. But on the technical level any <insert your DVCS>Hub would be at least nearly as good as GitHub. And git didn't invent DVCS.
Before everyone got onto GitHub, there was SourceForge and GoogleCode. Both worked well for a lot of people for quite some while.
Also, if you really want to, you can use the SVN interface of GitHub and never go through git. You could, in its time, also use Google code with git repositories but without the pileup if nice little things that make GitHub more than just a git hosting service