Dogs in good homes get very wimpy. Take my word for it. I take in rescue dogs - they enter intelligent, sly and stoic. They end up big babies, sleeping in our bed and crying and whining over every little thing. In that way, they are very much like humans. Anyone can see Trig’s dog is a well-fed, happy Black Lab.
First you claim that dogs *don’t* hide pain, and upon being corrected, you claim that dogs who *do* show signs of pain are being “wimpy” because they come from good homes?
How would you prefer a dog express pain? By putting their jaws around a child’s throat to correct it, as they would a naughty pup?
One cannot definitively claim that the dog is “happy” in that moment as the dog’s facial expression is not visible in the picture.