When I noticed a station I was pretty sure had moved from a DAB to DAB+ multiplex on my old radio, I did a Full Rescan and a Prune and it wasn't only still there but more DAB+ stations are now listing in the Station List.
They don't tune in, of course, but it's still bizarre.
All I can assume is that the Station List for some of the DAB+ stations is (mistakenly?) hosted on a main DAB multiplex. It's not the full list of DAB+ stations so it's only showing stations from one of the DAB+ multiplexes. There's a DAB+ in the car, so I know what's available here.
Unless some engineer made a mistake, or my DAB radio implements something in a non-standard way I can't see the logic of showing stations you can't receive? Maybe they reckon it will encourage people to upgrade?