The Realtracks are built from the "raw" realtrack files in the realtracks folders. If there weren't any sustained chords recorded, it may not be able to do that.

However, you may be able to use the "Hold" feature in the Chord Settings to force a Hold for the target Realtrack (selecting whichever Instrument track it happens to be on for the Hold -> Except) and see if you can force them to hold sustained chords that way. This would have to be invoked bar-by-bar, but this might get what you're after.

Have Fun,

--Mac