Sorry, I don't buy that they do not have pain. The specialists I use agree and their focus is on proper pain management. My regular vet is the same.
I think not medicating a dog after surgery is barbaric. Just because they don't carry on people assume they are not in pain.
I might also add that I have had many, many yorkies of different ages and sizes and never let them go without pain meds..and not one died from being medicated. If dosed properly there is no reason for them to die or suffer any ill effects.