I don’t believe this was an emotional support animal (like the famous UA peacock), just a small pet dog
I'm not sure about the description
I sensed it was so big that it completely filled a bag that was too big to fit under a seat, hence it took up aisle space until it was ordered into the overhead.
What is lacking for my judgement, was how evident was it that the case contained a dog?. Was the head at least visible? Was it drugged? Was it identified in a manifest?
Time for published rules for live animals to be fully identified and vetted before carriage ... not after boarding.