Strangeness.
I think we all see this happening:
Listening to phone audio, via bluetooth.
Stop the car. Turn off "engine".
Audio stops for a second, then resumes.
Open door.
Audio stops.
--
But since you are hearing audio even after opening the door, from the car speakers, that's super weird.
That said, I have seen some buggy behavior with certain podcast apps. For example, DownCast sometimes has trouble playing over bluetooth even though every other app and phone call is working fine over bluetooth. I wouldn't be surprised if your podcast app is having a strange interaction with the car.
Do other apps exhibit that same oddness? Or is it limited to one specific app?