Horner theory is not correct from everything that I have ever researched and known about the t-rex. Most animals who are predators/carnivores will not pass up a good dead meal anyday: that makes them scavengers as well.
This is exactly what the article is saying: the t-rex was capable of short bursts of speed. They are now speculating as to whether he was able to speed off as fast as orignally believed.
However, Horner and others present these theories as simply speculation. Unless something very ground-breaking occurs, we will probably never be sure about a lot of the aspects of these creatures lives: all of them. We, and men like Horner, can only speculate from the evidence put in front of them and then state their theories, either to be accepted or shunned by the scientific community.
bunny