Benny Morris said they were there to hide the number of deaths
He did not.

Here is the easily found report of the Kahan Commission.
http://www.jewishvirtuallibrary.org/jsource/History/kahan.html

From the same source

Maybe, but not from the actual Kahan Commission Report.

Kahan Commision report (unlinked, of course - I wonder why?) - hardly unbiased evidence

Sorry, but that is Israel's version of events and nothing you have found contradicts it.