Oh, bullshot. That means the removed lines such as HeardHulk, Zoey's "selfusehealth" dialogue when alone or Bill's lines (which were meant to be re-used for Crash Course, but were not) are.. all gone. Even the "SawSomething" which were also used in the early version of the L4D Intro!
Also, I personally think Valve should have kept the narrator lines in case you wanted to hear the Survivors' comments on the campaign by clicking on their storybook or their speech bubble. Also, if The Sacrifice has Francis saying the plane crashed, why didn't they keep the worldfarmhouseintro02.wav in the final?
Just for curiosity sake, where are these lines located?
I know Valve has a habit of leaving old things behind - like for instance, the old shotgun shell counter and the ammo pack texture. They also reused a lot of old assets from L4D1 when making L4D2 which they got rid of in the final product (the icon sheets, L4D1 music etc) so Chet's explanation is probably not far from the truth.