Last I saw, the back of Everest had been painted to resemble a temple built into the mountains. I found it to be an effective paint job from the parking lot (I have not seen it from Blizzard yet). While still obvious it is a flat back, it is much more appealing than the original beige wall or the dark stone colored wall that was tried first to cover it up. Disney is aware of their site lines, but they are also aware that spending millions to carve a mountain side for what is seen only from a few select distanct points is not money well spent. I thought the temple idea was quite ingenious and evidence to me that they were cognizant of that "bad show" of a flat back wall when Everest was being built.
The idea that "old school" Disney would not do such a thing is rediculous imo. At Disneyland for years, the huge green show building for Indiana Jones was visible from the parking lot until it was painted with 'trees' when DTD was built and the backside of Toontown is visible from the streets that circle the Disneyland Resort (I realize the space differences between DL and WDW make it more difficult to hide these things at DL, but it is all Disney Imagineers that build these things). Many of World Showcases pavilions' 'backsides' are visible from the main road that runs behind it, as are some of the Future World pavilions' backsides from Epcot's parking lot (primarly the bus lots come to mind).
Everest was built very much the same way Splash Mountain was built. While not a problem with Splash since the backside is not visible from anywhere, the idea is similar. Theme what needs to be themed. The backside of Everest is visible from a few points in AK's parking lot, the top of Blizzard and some of the top stories of Swan and Dolphin and the Contemporary with a zoom. The paint job to make it look like a temple built into the side of the mountain helped alot to cover the fact it was simply a wall, imo