It sounds like most other users install it that way too. Which surprises me, since I had thought the Linux community had started to move towards Flatpaks. But anybody who searched Flathub for Tor Browser, would have seen the flatpak with the Tor Project author listed as verified, and there would be no indication that this was in fact an unstable installation.

This was an official Flatpak from Tor Browser, so there’s no reason why it should be less reliable than the packages from distribution maintainers. Not to mention for atomic distros, flatpaks are the official way to install software.