Don't know how other jurisdictions do it, but in Ontario the old "drive clean" test was a "rolling road" sniffer test at two speeds, with the car connected to the computer via the diagnostic port, but not accessing discrete codes.
The new system does away with both the "rolling road" and the sniffer, meaning it can only "guess" or "deduce" if the NOX is within range - it cannot tell if the reduction catalyst is working because only the oxidizing catalyst is monitored by the secondary O2 sensor.
It is POSSIBLE that VW implements the "over-ride" whenever a certain sequence of events is performed that are substantially the same as the initialization procedure for running the test (There is a perscribed sequence of events that MUST be performed to get a valid test result) (like 20 many seconds at a particular RPM, followed by another given period of time at another RPM) which, if performed during the normal process of driving would also put the system in "bypass" for the anticipated duration of the test.