Epub2 being made instead of Epub3

I decided I should update myself a bit and start making epubs version 3 instead of 2. Using version 2.2.1 on Pop_os.

So I went into "Preferences->General Settings->Basics->Create New or Empty Epubs as:" and set the preference to Version 3.

Then (a couple of days later after several restarts) I used the ODT Import plugin to import a novel, and behold, I get a version 2 epub, with it's book.ncx and no nav document.

Any advice on what I'm doing wrong? TIA!