Jin Xuan is actually just a cultivar, so there's plenty of variety.
The "milk tea," from my understanding, happens from a cold snap at high altitude, but under more normal circumstances it has a little more of what you might be used to from a high-mountain wulong from Taiwan, although it still has much more of the amino acid smell and taste (i.e., it's still milky/buttery, but has a bit more of the leafy green and a slight floral aroma go to with it).
Of course, like all teas, the "milk tea" comes in a variety of levels of quality. Some will be genuine, "good" stuff ("good" depends on whether you like it or not), and then there's the cheap crap that's scented/flavored.
If you're tired of the "milk oolong" then you can try some of the other Jin Xuan wulong that's available -- zen8tea has plenty of stuff on the high-mid level of machine harvested wulong.