Hogwash.
At least one of the marshals has to brief the crew in person (among other reasons they board early). It also helps one member of the team ensure there are no suprises waiting for them already on board.
Forget about the fact that the gate agent has to be shown their creds at some point.
You do realize that all of this information has been discussed in pulbic hearings before congress and in major national newspapers, right?
See
http://story.news.yahoo.com/news?tmpl=stor...ghtbeeasytarget
Once again, security thru obscurity does not work.