Matching Alternates Using User Time Stamp - Not Working?

[DAWgEAR]

According to the Pro Tools 2020.5 Reference Guide, one should be able to add a clip to another clip’s matching alternates list by changing the User Time Stamp:

Reference Guide p.722 - "Pro Tools lets you exchange clips in the main play- list on tracks with matching alternate clips from other playlists associated with the same track, from other tracks, or from the Clips List. Matching alternate clips are clips that meet certain criteria. For example, clips that have the same User Time Stamp are matches."

Reference Guide p. 725 - "To change the User Time Stamp of other clips so that they can be available as alternate matching clips for a specific location, use the Time Stamp command in the Clips List menu."

I cannot get this to work. I have changed the User Time Stamp for other clips to match that of the clip that I want to create alternates for, and, no matter how I configure the Matching Criteria, these clips do not show up in the list of matching alternates.

What am I missing?

[DAWgEAR]

No one else using or attempting to use this functionality?