The poster was standing in an unsterile environment. So either you pass through gate security at F51 or you are taken by bus and dropped at the transit security which is downstairs next to immigration for passengers arriving at T4. I now see what having the bus at F51 would do. Basically they would do away with the gate's airplane duties and repurpose as the way to the bus. I guess that works though since they pay for staff and the bus I would bet they only allow people through who have boarding passes for a flight departing T4.

Sorry, by the time we got down there in the tour we were tired and just wanted to leave.