Lyrics will give you the actual text in the Lyrics tag if it exists.
Lyrics? returns a value to indicate what type of lyrics exist.
I can get values of Y [synched], Y [unsynched], or Y [synched/unsynched] which seems to be dependent on whether there are timestamps in the lyrics.
It also appears that Y [synched/unsynched] means "There are lyrics, but I don't know which type", rather than indicating the file has both.
Have a look at the type of lyrics tag in your two tracks in the Tag Inspector and you might be able to see why one highlights and one doesn't.
Bee excellent to each other...