I just picked this up today in store and it seems that the strap on the trio pouch was updated!
From what I can tell, the strap on the original set had a u shaped ring at the end that didn’t open but that the three o rings clipped onto. This meant that the strap could really only be used with these three pieces.
The new version has a clip on the end (that actually rotates!) so that the strap can actually clip on to any other bag too (ie: you could clip it onto the pouch included with neverfulls). New version can be seen online.
A nice upgrade as it makes it slightly more justifiable at the $1390 price for four completely separate pieces.