Disable session restore does not work

I would like to disable automatic session restore completely. When I restart my PC, crashes or anything like that, I do not want Firefox to restore my previously opened tabs or windows. When I open firefox after a system reboot / crash, I want to only open my default home page. Only if I manually click ''History > Restore Previous Session ''should firefox ever restore my session, otherwise never restore my sessions. I tried unchecking ''Settings > Startup > Open previous windows and tabs'', and also tried following this article: https://support.mozilla.org/en-US/questions/1182594 My sessions still restores after my computer restarts or crashes. Why do I want this? When I reboot my computer, I want a clean slate to start from scratch, not the dozens of pages (and other software) I had open from my previous session. I am running linux mint btw.