I disagree. He's under oath. He is shown a pic in which he does Not see the sign. He says so. That is Truthful testimony. The man is a grounds keeper operating out of a shed behind the Pergola Shelter. You're Not going to hear him expounding on The Theory Of Relativity.
I don't understand why something as crucial as the Stemmons freeway sign would be removed given that it would be needed for reconstruction purposes. Once removed, it made it much more difficult to accurately place JFKs limo at the time of the SBT.