doesn’t libre auto back up every five minutes?
No. It saves autorecovery data in case Writer or the PC crashes while Writer is open. If you close Writer without saving, your work is gone. It does give a warning, asking if you want to save your work. If you don’t, it assumes that you don’t want to save it.
To add to @anon87010807’s answer, the backup and Autorecovery strategy is explained in this LO help document.