Previous session tabs reopen regardless of settings if Private Browsing is opened first

[3e33]

What happened?

Waterfox version: 6.5.1

Steps to reproduce:

1. Close all Waterfox instances
2. Open a normal Waterfox window
3. Open a website
4. Keep the tab open, close the window
5. Open Waterfox in Private Browsing mode
6. Open Waterfox again in normal mode
7. The previous session's tab will re-open

This is even though "open previous windows and tabs" is turned off in settings.
Not only that, but this happens even if all the sessionstore variables are false in about:config.
Seems as though Waterfox saves your previous session regardless of any settings whatsoever.