This is a bug that has been transferred from TSW to SWL. When you use the quality filter, certain items that is for sale in the AH, and that are within the parameters set, do not show up.
The easiest way replicate this is with Ashes of Shriven Souls.
If I select Talisman and search for shriven I find 5 luminous and 4 radiant for sale:
Now, if I add Quality = Superior and search again, all the radiant ones disappear:
I don’t know if this is an “per item” bug (i.e. Radiant Ashes of Shriven Souls is missing their quality) or if there is something else at play, but at least in TSW this bug was true for several items in the clothing category.