CL300 cant open your link because a very slow and volume limited connection right now. However, Iīm familiar with the fact that 'they' (Immigration and customs) can do random check whenever they like.
USUALLY they donīt do these on departing aircraft.
However, the reason here is not Schengen in switzerland, but the lack of Schengen in the UK, and the totally pigheaded approach british immigrations puts on the .... immigration.
However, has anyone seen that in a transiting Airliner? Unloading all bags etc?