The counterargument is that a SAAS platform like Github's interests are in the ongoing viability of the service, while my interests are only about in my data in the service.

Those are only somewhat aligned, as anyone with a dispute about terms of service can tell you.

> which can be a bit much for one person who's self-hosting

If your repo serves one person, why do you need your repo to be hosted in public at all? `git init` and a backup are all you need.