Came across this on an FAA publication dated 3/12/12, maybe this is what you saw with everyone exiting the plane through the main entrance? (page 19):
"
4) A test method referred to as a “platform” or “ramp” test has also been used to assess the crew's ability to manage flow of passengers for a given interior configuration. Appropriate test conditions and pass/fail criterion need to be discussed with and agreed to by the FAA for each new situation."
Document here:
http://www.faa.gov/documentLibrary/media/Advi...803-1A.pdf