I am pretty familiar with Schiphol and the walking time from entrance to gate is about 15 minutes (7 from BA lounge to gate), that said I walk fast!

I always assumed on the basis of watching closing flights - and I may be very much mistaken here - that once doors are ready to close but for the missing passenger(s), at T5 at least, a sort of "race" ensues whereby the pax are called (often multiple times) while the offloading search process continues. This seems to be the pragmatic way to deal with it, although lacks the "teach them a lesson" aspect some might hope for as the latecomers breeze up to the gate.