I would recommend opening a case for this. There is some information we could gather and take a look at and see what is going on
I think the root of this is that you are trying to use the inventory settings to exclude a value that isn't populated by the inventory scanner. It shows in the list because it is part of the database schema, but data is reported by the software distribution engine not the inventory scanner and therefore it does not get blocked.
It is still an issue for you but perhaps this might help a bit in understanding why this would be happening.
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Quite a helpful insight.