Admittedly, it has been several years since I used an iPhone - but I don't remember it ever telling me that slide-to-delete was a thing. I literally had to ask on Twitter to find out - https://twitter.com/search?q=delete%20podcast%20from%3Aedent...
I agree that there are some things which work best hidden - pull to refresh, for example - but it needs to be consistent and explained.