True, but in this case with SQLite, there's unlikely to be much of a difference because there isn't the spare time available when waiting for a separate database server. I don't know what providers are good for a $10/month instance these days.
How are you spending any non-negligible time reading from SQLite at 12 requests per second though? That would mean you’re spending something like 50 ms per request on reading from SQLite.
Development runserver has been multithreaded by default for over a decade. I think you need to go back to major version 1 to see it single-threaded by default. Maybe affected by the GIL though.