This, to me, is a specious argument - sounds good, but how does that compare to the teeth of what we used to call a brontosaurus that was 100% herbivore? Another thing that I think is a great comparator is body mass and shape.
It would seem to me that a herbivore would require a rather sizeable 'digestion' engine for all those 'leaves' - big stomach, large intestinal tract, etc. I can see this in the erstwhile Brontosaur, but I fail to see it in a T-Rex. Likewise, I don't see the long neck and tree-top reach, nor do I see the same forefeet to support the massive "digestion" system. Instead, two little vestigial arms with claws that are, at best, usable in manipulating a kill in preparation for eating.
Sorry, but I just don't buy the sharp toothed herbivore argument at all.
Actually, it doesn't even sound good. Pointed, triangular teeth are good for puncturing and slicing. Flat, blunt teeth are good for stripping and grinding foliage. For slicing through broadleaf plants, you want straight-edged incisors.