Apparently there is an ongoing thread about a very similar issue here:
https://forums.unrealengine.com/development-discussion/c-gameplay-programming/57024-inherited-component-details-not-showing-in-blueprint/page2
Epic has since opened a bug report, and are working to resolve it. I hope this will resolve the behaviour you see described here, too.
It’s also possible I just set something up wrong. I’m still working on a situation much like this right now and trying to figure out how to get my UComponents to show up in a derived BP’s Details panel for them.