This is just odd because I’ve never seen it before.
As you can see, the song description is listed underneath the title. I haven’t noticed this in looking at thousands of titles in my library. Here’s the metadata from Allmusic.
Is this normal?
I’d think that’s to be expected if there’s an allmusic description available for a composition. Or maybe I’m not getting what puzzles you. 
Hi @David_Gibson,
Yes, if a composition description is available from one of our metadata providers it will typically appear here.
Cool, I’ll have to look for some others.