I was also thinking maybe the dad stayed longer because that's when Rocco was put down so dipshit didn't immediately fly up and try to record them doing it.That clip is telling. It's all starting to come together.
I think you all are right, the "big surprise" is a dog. He must have got word that Rocco was going to be put down before the parents arrived, and this is his big opportunity to guilt Casey to get her to cave (hence why he needed her permission).
The entire "Rocco series" will include the journey of him getting a dog to help "process his grief."Nothing is too low for this family.