Now if I just change these two lines of code in the Master script - it works.
partName = "19050 Window reveal"
! n = REQUEST ("ASSOCLP_NAME", "", partName)
The arrays surfaceTypeDesc, surfaceTypeIndex, surfaceTypeValue report the same values in both cases (as far as I can tell) - but in the first instance, I only get the option "Object Override Surface", but in the second option above, I get all three. See attached images.