Hovering over various tracks in a playlist or Playing Now, displays the above message in the information window that appears. Some tracks display it, others don't. Those that do and don't usually are consistent through a total album of tracks.
I've never created any stacks, and the files are HD from HD Tracks or similar. Most of the time, but not always, this message will not appear on tracks that were ripped from CD. The bit rate of the track seems to have no bearing, and right-clicking on the track offers no undo capability for the dual stack.
A couple of examples that display the message are Daft Punk - Random Access Memories, Christy Baron - Steppin'. However a Count Basie & His Orchestra - Breakfast Dance & Barbeque, does not, nor does the recently released HD 2015 Remaster of 5 David Bowie albums from HD Tracks. Some album titles do and others don't, yet there seems to be no common denominator.
I believe this started fairly recently, or I've just never noticed it before.
Is this a bug or anomaly of some sort? Or asked, differently, what does it mean?
Thanks.
--Bill