The language reads:
Any place within the ski area boundary that contains cliffs with a minimum 20-foot rise over a 15-foot run, and slopes with a minimum 50 degree average pitch over a 100 foot run.”
Every double black at A-Basin is extreme terrain with no ordinary double blacks. It's extremely misleading and IMHO gives a skier a false sense of confidence when the terrain is not infact extreme. For example, "Land of the Giants" is rated Extreme terrain, yet if you stick to your skiers right (not talking about the traverse, but the actual trail), you won't hit any cliffs, and it's no harder than a blue. Technically this qualifies as ET though since there are cliffs on this "trail"
I think some skiers go on it just to say they've skied extreme terrain, so the label acts as a magnet instead of a deterrent. I think having signs on normal double black that say "danger - cliff area" would be much more effective in discouraging skiers unsure of their actual ability. Instead skiers want to rack up gnar points and brag about being "extreme"
I don't want to start a pissing contest between Colorado and Tahoe but when I skied Squaw Valley, I learned pretty damn quick to respect the "cliffs" discs that were above the Silverado bowl. Even though every trail map says its ratings are relative to only that particular resort, I can see how a skier that went on "extreme terrain" could get themselves into trouble as a ski resort that has 40+ foot cliffs everywhere like Squaw.
All in all, I think "Danger-cliffs" speak louder and more directly, and is more universal that extreme terrain.