Lists only sort on the first vertical row. Anything placed in the additional rows (with neither "Accept.." button pressed) is ignored. Additionally, I am using them inside a diamond transport pipe. This is limiting the usefulness of lists as you can only place 6 unique items in one list, rather than using the full 42 spaces.

Using the Accept Variations or Accept Equivalents buttons do work to sort the items added by the UI.

Using Buildcraft 6.3.3