The difference being that Monks could be played by almost every race, and there was nothing unique about the class. In fact it became rather generic, because there was no real difference between a Pandaren Monk and BE monk, so why would you play the Pandaren?
The Tinker on the other hand should have models and animations for exclusive for each race just like the Druid class. Goblins, Gnomes, and Mechagnomes should have unique mech and robotic summon models for each race, and that would give the class more flavor, and gives the player more reason to choose one race over another. Again, a situation nothing like what happened with Pandaren and Monks.