My half German Shepherd/Golden Retriever (also half the size of both breeds) also barks at dogs on TV (I look at this as a sign of intelligence), at the same time leaping 3 feet in the air. If you say dog he will turn and check the screen, he also barks at any animal with 4 legs. People are all good to him.
I think he can’t tell the difference between the TV and a window.
Can’t wait for the Puppy Bowl.