While I haven't read the book in question, or anything by Rand, I do know a bit about artists.
The basic premise is correct that the artist doesn't have to submit to the demands of the customer to produce their works but taking this from the few to the many, in the case of architects, is a logical fallacy.
There is no guarantee that an artist with this point of view will ever make a single dollar from their creative efforts but history has shown that the truly creative ones are appreciated for their vision. Frank Lloyd Wright or Gaudi were perfect example of this, you either gave them complete creative control over a project or you went somewhere else (presumably since I don't know the exact way they dealt with clients). Someone who wants a generic strip mall designed isn't going to go to an architect of this nature but they had a ready market for their services.
They did in fact serve the needs of the client contrary to what Skousen is claiming because the client desired their artistic creativity along with their competence as an architect.
Destruction of private property is obviously the wrong way to go about a dispute with a client but I guess you have to give some artistic leeway since it was a fictional piece after all.
Criticizing the economics of a novel seems about as productive as dismissing the basic premise of Battlestar Galatica because the Cylons don't have a market to set prices and wouldn't be able to allocate their resources in a way to be able to sustain their pursuit of the Colonials.