Sure, but users understand the risks. If the dev throws up a splash screen saying "Proceed at your own risk. Your account might get locked," then they can't be held morally accountable for that.
I don't know. It would've been an interesting experiment to carry to its natural conclusion.
On one hand, I agree with you, on the other hand, I'm 100% sure some users will send angry emails to PocketCasts and demand refunds because this third-party app didn't work well (or they couldn't figure something out, or any number of things).
I think it might be a different story if you didn't have to pay to use the web UI (and consequently the desktop app). That's a pretty big risk, and would mean having an awkward conversation with a support person about why you were violating their ToS, and also not being able to use the web or mobile apps anymore.
I don't know. It would've been an interesting experiment to carry to its natural conclusion.