Spotify is actively and aggressively trying to be the ones to break podcasts by having their spotify exclusives.
Even things like Patreon bonus episodes aren't a problem -- they still are sent out via RSS. Still use the interoperable standard. You can even share the URL with people you know, if you feel like it.
The bad actors creating true app-exclusive content need to be called out, shamed, and stopped. Even if it is NPR.