@FinchHaven How is Phanpy a browser add-on? Phanpy runs in the browser the exact same way as mastodon.social or any other instance runs in the browser. Just point your browser to the URL, you don't have to do or install anything extra.
So it's more like asking why can't this model engine installed in this car take me anywhere when this other model engine installed in the exact same car can, when I know both engines runs fine and they are both installed correctly in the same car.