Originally Posted by KLouis

Pier D is the only one with an upper floor. Thus, if they were routed through an upper floor, as you wrote, it can only have been pier D!

Central Security is not by pier E but in front of pier D. You can only access it, though, coming from the CI, etc. area, as it is separated from the non-Schengen sterile area from the immigration booths. When deplaning you are in the sterile area where shops, lounges, etc. are located and you can walk freely without any controls from pier (gates) D to pier (gates) H. For piers (gates) B-C you do have to go through immigration as well as a "smaller" security check.

To have a putative secondary inspection, one would have to be met by the immigration officers at the gate. At any rate, any passage through the upper floor implies an arrival from a Schengen country. I link here to the official map of Schiphol airport where one can see what I described. The graphics are really bad, mind you...