That's not the case.
I just copied url to post I made to 'everyone (public)', set my browser into private mode, went to that url and I could my post just fine.
Thanks for clarifying. It's been a while since I clicked on a Facebook link. When I tried it just now, you are right that direct post URLs will work. But when browsing a public page or profile, there are pop-us that obscure the rest of the screen as you scroll or hover over links.