I also buy from Zoo plus and I also bought the white 96 pack of pouches, and asked the same questions that you are concerned about.
As you rightly say, each pouch has the words "Factory use only" on the back.
If you look just above those words, you will see an electronic logo, the kind that could be scanned with a scanner or smart phone.
I enquired at great length about this and the following is what I was told :-
The electronic logo is part of quality control, to ensure that only pouches that have been approved for use are included in the package.
The words"Factory use only" refer to the logo itself, not to the contents of the pouch.