Well of course. In my business, you don't look at the visually obvious and make declarations.
As I said, that pretty sounding description full of assumptions you posted doesn't hold up to fact. The 'silt layer' is no were near thick enough to account for the amount of earth "erroded" out of the grand canyon. it's more consistent with the silt accumulated by a lake that once existed in the area.
I.e., everybody's wrong but you, huh? Why is there no historical record of a lake there? Why were steamships able to carry passengers from the Gulf of California to Yuma, Arizona if it was a lake and not a river delta? Why did people describe canoe trips through a "bewildering maze of green"?