I hadn't ever heard of this. Here is a statement from the Tor project for anyone else wondering what this is about:

> We automatically resize new browser windows to a 200x100 pixel multiple based on desktop resolution which is provided by a Firefox patch. To minimize the effect of the long tail of large monitor sizes, we also cap the window size at 1000 pixels in each direction. In addition to that we set privacy.resistFingerprinting to true to use the client content window size for window.screen, and to report a window.devicePixelRatio of 1.0. Similarly, we use that preference to return content window relative points for DOM events. We also force popups to open in new tabs to avoid full-screen popups inferring information about the browser resolution. In addition, we prevent auto-maximizing on browser start, and inform users that maximized windows are detrimental to privacy in this mode