Is a play script just an "information delivery system"?

In the previous post I provided a link to the book: Off Off Broadway Festival Plays 34th series. One of the short plays in the book is called
"Realer Than That" by Kitt Lavoie.  Kitt is the Artistic Director of The Cry Havoc Company, which focuses on developing new plays. www.cryhavoccompany.org

 If you follow the link you find the web page of Cry Havoc Company and the Cry Havoc Podcast, a series of recorded discussions of subjects related to developing new plays.

http://www.cryhavoccompany.org/01CRYHAVOCWellWrittenPlays.mp3

This is a link to an mp3 recording of a discussion of the "Elements of a Well Written Play"

It's interesting subject matter, complete with the assertion that a play script can be thought of as an information delivery system. A script is also described as a blueprint of a production, and as a skeleton - the structure of a body whose muscle, skin, hair etc. is provided by the director, actors, and other artists associated with a production of the play.

Playwrights may be more than a little taken aback by this. But it is an idea that is firmly dug into the thinking of theater people who also believe that the playwright often doesn't actually understand what his/her play is about, and it is only after the director and the cast get their hands on it and work with it that the play within the script emerges.

I wonder if David Mamet eagerly awaits the magic that a developmental theater company performs on a new script that he might hand over to them? I've also heard it said by some well known actors and directors that their sole purpose in producing a play is to serve the vision of the playwright.  What do you think?