That’s called dogfooding, not self-hosting :)

Let me get this straight though: I’m not saying no project self-hosts their code (eg. IIRC both KDE and Gnome do), I’m just saying that the majority of FOSS projects (including those that are dedicated to self hosters) does rely on some sort of third party to host their source code.

I don’t think it’s fair to criticize a FOSS project just because they rely on a third party (even commercial ones) to publish their source code.