What does the Sandy Bridge CPU clock down to in order to help put this into perspective?
SB and IB both clock down to 1.6GHz, so clocking down to 800MHz is essentially going down to 1/2 of the idle clock. If paired with even lower voltages at 800MHz then it would mean massive power savings for 'always on' equipment.
I use my rig as both a gaming/production rig, as well as the home file server. Because of it's file server uses my machine is not ever allowed to go to sleep. Sandy Bridge is not a huge power hog, but my next upgrade should be to Skylake or Skymont in ~3-4 years, and the idle power on that should be essentially nothing.
The bigger issue for power use on computers is the GPU. My wife's last upgrade went from a Core2Duo with a 8600GT to an Ivy Bridge i3 with HD4000 graphics. Sure, the CPU takes less than 1/2 of the power at idle, but dropping the GPU made for massive gains in power consumption. Even my own rig went from a 9800GT to a GTX570 which has a pretty big drop in idle power consumption, but moving to a chip just 1 gen later would cut that in half again.
I would imagine they're only restating this, as in the chips will still be overclockable via BCLK and that the base feature will not be removed. This is very likely one of the locked CPUs. I don't see a reason for them dropping the whole "Unlocked" CPU lineup due to the fact they sell like hot cakes, and they really don't lose money off of it (it's not like every guy and lady is killing their CPUs left and right with overclocking).