Question about metadata-based text cells in Book Module

Lightroom Classic CC 9.2 on MacOS 10.14.6.

I'm working in the book module attempting to create custom pages with more than one photo and freely positionable metadata based text fields (such as caption) for each photo.
The original Photo Text objects won't work because aren't freely positionable.

The new "Photo Description" cells that were introduced (I think) with the custom layout are freely positionable and have a capability to add metadata based text.  So far so good.

It also appears that if I create more than one photo cell (right click -> add cell -> photo) then create as many photo description cells on the same page (right click -> add cell -> photo description), then the photo description cells appear to be asociated with the photo cells in the order they were created.  For example, the caption for the photo in the 1st photo cell created shows up in the 1st photo descrpition cell, etc.  If there are more photo description cells than photo cells, then the metadata fields only work 1:1 with photo cells.

However, there appears to be no way to modify or validate which descriptions are tied to which photos (other than adding photos to the page).

My question is whether this is actually a documented and supported feature or an accidental side effect that could go away in different situations or future releases.  I can find zero documentation or discussion on Adobe or the even web/video searches for metadata populated "photo description" cells. 

This is GREAT feature if it's real, but could turn into a waste of time if it isn't reliable or goes away.
Any decisive answer would be appreciated. 

Thanks,

Don