Opening the browser app makes it easier for people who e.g. edit TMDB data to switch back and forth between the browser and SeriesGuide, or to easily open multiple links. For “regular” users nothing really changes as going back still will close the tab and return to SeriesGuide.
The only benefit of using the in-app browser was avoiding an app switching animation and not having a separate entry in the app switcher.
Instead of adding yet another settings option I decided to go back to the standard behavior.