I will start out by pointing out that this is an important find. Unfortunately, the authors simply assume that this is evidence of evolution. There’s no reason why it wouldn’t be an example of design, however. In fact, I’d go so far as to say that the design hypothesis fits better. Why would TATA in a gene’s promoter tend to make it evolve than other genes? Aren’t the mutations that drive evolution random? Does the TATA sequence somehow stimulate mutations that are supposedly random?
Design on the other hand can be thought of as a code, like a computer program. When the TATA sequence is read, it triggers the code to change and help adapt the gene. In other words, it is a command to change the gene. This makes more sense than the evolutionary scenario.