Call it what you will. I think the distinction is valid, as working animals have a job, and treatment standards for pets don't apply. Working dogs need to be able to hold it in and/or stand up to a bit of being jerked around at their handler's convenience, without getting distracted. They're trained to put up with this stuff.
It might be true that impatient, testy handlers would get more out of their animal by behaving differently, but there's a big difference between that and treating an animal with outright cruelty.
While I have no reason to believe the original story about the dog, and would be inclined not to believe it as a properly trained guide dog would not need to have the lash yanked "all the time" and the commenters claims
That said I also believe your statements about "treatment standards for pets don't apply" is also completely wrong as the implication here would be that service animal should be treated less well than pets because they are "working", this is unbelievably ignorant and wrong on many levels.
Abusing a service animal simply because it is a service animal is wrong.
It might be true that impatient, testy handlers would get more out of their animal by behaving differently, but there's a big difference between that and treating an animal with outright cruelty.