I am not from Texas, but exclusively utilizing protected or secure radios to use as an officiating tool makes perfect sense. It is not hard for any fan (or press) to pick up the radio conversation. All that is needed is a portable scanner with frequency scanning capabilities. Go to any NASCAR event, and you can see how easy it is.
With the way social media works today even an "innocent" comment can be misconstrued, and taken out of context. I would not want any of my conversations with my crew mates to potentially be made public. This rule not only seems reasonable, it is probably the only way to go.
It seems prudent that the radios in use be secure, or officials just communicate the "old fashioned" way.