is 18,700 feet high, and doesn't have any major moraines, and rises out of a plain (it's a volcano, of course). And it's in Mexico, so the glaciers are higher up. Also, Muztagh Ata (Tibet) is 7,500 meters (24,600 ft), and it rises out of a plain that is only 4,500 meters or so (14,700 ft).

Of course, there's no evidence that the Misty Mountains are geologically analagous to anything in Tibet, and certainly they're not Mexican volcanos. They are supposed to be snowy, and the Sierra Nevada are just barely snowy despite being, as you say up to almost 14,500 feet. But then, the Misty Mountains are also probably farther north.