Yes I've heard it before, probably on this thread. The Planet of the Apes was originally meant to be set in a futuristic sci-fi society same as the novel but the make-up effects used up so much of the budget that in the end the apes were living in mud huts in the dessert. Not that I think there is any kind of resemblance to the P+G film, they are obviously people wearing masks.
Could it be some kind of early prototype costume made by Chambers for the film that was shelved? A possibility, but to my knowledge there is no evidence Chambers and Patterson ever met. Without knowing what Mr. Chambers was like as an individual, I couldn't say whether or not he would want to get involved in a hoax when he had a successful Hollywood career.
And if it was something made by him then Philip Morris is/was lying...
Rick Baker and John Chambers are mentioned in relation to this in The Munns Report (Bill Munns - yet another creature suit effects guy)
on this page -
http://themunnsreport.com/
go to PDF downloads, click on 'A True 20th Century Mystery', their involvement starts on page six.