But let's say that you now go back to your first browser window, which is still on an old screen, and try to log out of that window. Because you're not *actually* logged into the same session that you were back when that page was loaded, you'll get the confirmation screen [...]

Yes, the one that will often say something like, "You have multiple browsing sessions open on various computers - expire all sessions?" I get that one often because I switch IP addresses a lot to stay online (one signal dies, so I'll switch to another that's still working while I'm still logged into DW), which messes up DW's tracking big-time (the system thinks I'm logging in from more than one computer/location when in fact it's all coming from the same place - my kitchen computer, in fact). :)