Sure they do. The mechanical nature of the Tinker class makes it unwieldily for anything except for the shorter races. Having a mechanical backpack that transforms into a mech for example causes significant size issues.
That's not a problem with a Monk class, so while it's Pandaren-based it can be other races without issue.
For the sake of argument; If Blizzard wants larger races to be in this class and wants a mech form, they could opt for an Ironman style mech form;
Where the mech is the top half of their body. At one point HotS adopted that form of mech.
But that would still require the mechanical backpack, and I simply don't see that being available for other races.