It takes up quite a sizable amount of the screen, too, so anything in the corner is effectively hidden without interacting with the popup. These pop-ups have been the bane of my life.
There was brief time when Pinterest automatically logged in Google account users if you made the mistake of clicked an image in Google search results. Popups sound downright civilized and principled by comparison
It looks like the pop up is part of the browser UI in Chrome, and displayed as part of the website if using non-Chromium browsers. I block ads and don't use Chrome, so I don't see any version of this often.
This happens exactly because you're not on Chrome. For some reason the sign in with Google pop up only triggers on non-chrome browsers. Especially on Firefox.