> wouldn't hosts have the original source material that they uploaded
As far as I'm aware, Apple never resurfaces the audio after it's uploaded, even in your dashboard. Even if they did, making someone manually download and reupload every asset for potentially hundreds of episodes is sadistic. Moreover, you physically can't leave, because your listeners won't follow you to your new hosting service.
> These users aren't there just for generic hosting, but also for the network effects.
The network effects are limited to an app with only 40% of the market. Outside the US, that number is even smaller.
> just that there is fairly old precedent
Every podcast hosting service ever has allowed you to leave their service.