Occam's razor states that the explanation that requires the fewest assumptions is most probably correct-the simplest explanation IOW. A mouthful of exceptionally large, sharp pointed serrated shedable teeth most simply describes an animal that kills other animals and then eats them or that finds them dead and then eats them or both. In today's animal kingdom, we need only look at the great white shark to gain an idea as to the dietary habits of the T. rex. The great white shark is a modern apex predator that will also not decline to eat carrion should the opportunity to do so arise.
Furthermore, fossilized duckbill bones have been found in fossilized T. rex scat.
(1) I'd like the article. (2) That does not prove that the diet regime started that way. (3) Occam's razor is probablistic and can fail. It is not proof of anything.
But, here we go, and I don't want to follow it. Your system and mine, about origins, are incompatible. They cannot be blended. Trying to do so only produces endless debate. At this point in time, there are no logical winners.