I believe that I have found a bug, but wanted to check this by the Community to see if I'm missing something or if there are some additional creative workarounds that we could employ in the future. I've created a simple illustration of what we are encountering for the screenshots below, but what we are doing in reality is on a larger scale.
It seems that formulas do not adhere as expected to subset formatting. For instance, I have the below module dimensioned by a list "Company". There are two line items: "Geos Mapping" where a manual assignment is made of exactly one item from the Geos list to every item in the Company list and "Geos Lookup - Excluding EMEA" where I want to only pull through from Geos Mapping where the selected Geos item is not in a particular subset (namely, a subset I created that includes all members of the Geos list except for EMEA).
I would expect that EMEA does not show up in "Geos Lookup - Excluding EMEA" as it is formatted as the subset that excludes EMA. However, it disregards the fact that the subset excludes that item and populates in every case.
Workaround: Add in IF/THEN logic with a LOOKUP - can be completely formulaic and gets to the expected answer
Since we do have a workaround, we are able to continue for now. But I am curious as to if others have encountered a similar issue and what workarounds you employed. And, of course, if I'm just doing something wrong and it's an easy fix then let me know