They wouldn’t do it to retain the small audience. They would do it so they could safely deprecate even more old devices. It makes life easier on the app engineers when they can focus on fewer devices and OSes. Less testing. You can use more modern libraries without a bunch of “if” forks. Sometimes the oldest 2% of your users can represent 15% of your effort. But 2% of users is a lot to drop.
That’s where the 3rd party app would come in. It would quiet complaints and allow content contributors to be retained, without any maintenance. Basically it would de-risk some moves like only supporting phones from the last 4 years, and nothing older.