The EU does allow opt-out at the entry to the "sterile" area. That seems to be the differentiator, because the scanner for SSSS awardees is not at the entrance to the sterile area. In Terminal 2 there's a separate section well inside the sterile area that the SSSS awardees are escorted to, AFTER they have been through the standard screening. That section has its own scanner, just for SSSS screening.

Unlike the US, SSSS awardees are not treated differently than other pax in primary screening (where it is possible to opt-out). Only after you have reached the gate area and attempted to pass through the final BP/passport desk are you shuffled off to secondary.

So, it truly is Secondary Screening, rather than the main checkpoint goat rodeo I experienced in DFW last week.