That image is
not a pandaren brewmaster, that's a
pandaren "transcendant". Yes, that's the name of the class. And they're just, well, "transcending" geomancers, not monks. And they also do not "split" into three separate pandaren, but actually individually take on the aspect of a given element, like a druid changing forms.
As for "brewmasters" in the RPG, guess what? It's not a monk. Literally just a "brewmaster". One who uses the magical-like effects of his specialized brews on himself to fight drunk, but not a monk. A brew afficionado who really knows how to make some potent spirits.