Weirdly unrelated directly to software updates, I've now noticed podcasts using mobile data, despite never allowing it, keeping the toggle off.
It's the first time I've used the podcasts app for about 5 years, and only use the downloaded ones, so never a need to have the toggle on.
I think apple just have really bad metering / control of when data is allowed and by what apps / the system - or else the phone is counting data used during hotspotting to the mac - possibly it somehow gets stamped with the apps usage and is assumed to be for the iphone app.... just wild speculation - no idea how hotspotting and app metering work.