Depends on to whom. If you're explaining to your grandma, a small child, a co-worker, or a student under your tutelage, you probably don't want an explanation that relies on reference to a porn site.
And if you're explaining to a novice developer or to an IT person who sometimes might have to work with Git, they deserve an explanation that leaves them with a basic understanding (or at least the names) of the kinds of things Git and GitHub are (VCSes and SCM forges, respectively), not just an inkling that GitHub is not unique in being 'a place to host (some?) Git, whatever that is'.
So... if you don't mind that it suggests 'GitHub is for uploading Git(s)', that line is an okay way to teach 'the difference between Git and GitHub' to non-technical, non-elderly adults who don't really need to know what Git is (and don't work with you or study under you).
That's an explanation of pretty damn narrow usefulness, to put it generously.
It is pithy and memorable, though.
The Nix daemon itself still uses root at build/install time for now. NixOS doesn't have any built-in sandboxing for running applications à la Docker, though it does have AppArmor support. But then, NixOS doesn't generally have applications run as root (containerized or otherwise), unlike Docker.