Can’t answer to Tor—haven’t even tried it in years, but I know on Windows, Firefox totally ignores the whole “reopen tabs on restart” pref if you close the last window via the red X in the corner. You have to use control-shift-Q or show menus and select File->Quit if you’re going to quit it in a way it understands as requesting you to reopen the tabs again next launch.
As an example of this, I believe SexyCyborg got in trouble for reporting on leaks via people’s 3rd party Chinese language keyboards. So her theory is that the keyboard apps people had installed leaked data when Hong Kong protesters were communicating with the press, rather than the actual Signal app. But… as stated above, people have to take responsibility for their device and in this case, they had chosen to install apps with leak issues into the communication process.