I mean it gets the point across, regardless of the service dog or a pet(which shouldn't be in the TSA security line in the first place cuz generally airports will have a designated drop off or require Kennels) , in this case it doesn't matter how dense you are, it's clear: do not pet the dogs, if the reader wants to say that it means no petting dogs on the entire trip, the airport doesn't care as long as you're not petting the dogs at the airport, and therefor not getting in the way of procedure or causing a potential safety issue for the port