I don't know if this is true or not. Though the sheer amount of increase makes it sound fake to me, I do seem to remember that a while back someone (maybe it was someone from IBM) stated that the CPU was intentionally underclocked.
If that's true, and Nintendo has now done this, I not only would expect that the new clock rate likely not exceed 1.8-2 Ghz or so, but that the system would likely (through this update) continue on at the lower clock-rate by default, but developers would now have access to bypassing that default and triggering a supercharged mode.
So if you're playing Nintendo Land for instance, it's your regular old Wii U settings. But if you are playing some game by a 3rd party developer in 2014, popping in the disk of such a game would temporarily move the console from default. Make sense perhaps?
Sounds rather unconventional for a company like Nintendo, but with the original Wii being so underpowered, perhaps they built in a safety net, where as a company they say, 'Hey, we think that this is all you need, and the wattage will make the console nice and energy/environmentally friendly. But just in case, here's the emergency switch...'
Should have flipped it months ago imo.