I think the website compares it to BluetoothLE which is a really low energy. But typical BluetoothLE data rates are much much lower than 250Kbits/s.

I'm still surprised that they can bring it down to lesser active current draw than BluetoothLE which was designed for low-data rate, low current draw, short distance comms.

Edit : Here's a app note on real life current draw of TI's BluetoothLE solution.

http://www.ti.com/lit/an/swra347a/swra347a.pdf

Edit 2: Here's another research paper comparing ZigBee and BLE solution's current draws. ZigBee is almost an order magnitude larger in current draw.

http://research.microsoft.com/pubs/192688/IWS%202013%20wirel...

Edit 3: Old but good presentation on power usage in 802.15.4. http://www.cens.ucla.edu/sensys03/sensys03-callaway.pdf