It seems that if I have "Restore Locked Tabs" checked, but do not have any locked tabs, that when I close and reopen Windows Explorer, QTTabBar does not restore all tabs. It properly restores tabs, however, if I do not have any locked tabs *and* I do not put a check mark in "Restore Locked Tabs."
If I do have locked tabs, it functions as expected and restores them.
(And by " . . . does not restore all tabs," I mean that it only opens with one new tab in Explorer's default location ("Libraries," in my case.)
I'm sorry to double-reply to myself, but to be very clear, it only opens Windows Explorer to one tab, in the default location. Also, it seems that in restore-locked-tabs mode, it forgets all other tabs, and only opens Explorer to the remembered locked tabs, plus a tab for Explorer's default location.
I think I might prefer that locked tabs only prevent any other applications from closing a tab/Explorer location I don't want ever closed, but to always restore all tabs, whether they were locked or not locked. On the other hand, mabye the functionality that opens recently closed tabs offers effectively that.