pushState under certain circumstances a dummy entry, so that when the user clicks back to leave the SPA, there's that buffer for us to detect popstate, show the modal, and then flip a boolean that will fix things up to allow back navigation afterward. However, it seems browsers have begun trying to skip duplicate entries when back is clicked, seeing discussions such as https://github.com/WICG/interventions/issues/21 and https://github.com/whatwg/html/issues/7832. I've thought about potentially doing some kind of client-side routing (we use React Router), and a <Prompt /> that'll get me there, but that seems like a bad idea both because it's hacky and because I don't believe navigation blocking are available in the same way in the newest version of RR.