What's even cooler about this method is that the sensor is used only once, at the very beginning. The imaging sensor isn't even used when performing the phase detection AF afterwards.
In contrast, using live view continuously as with FoCal, etc., slowly warms up the sensor and increases the noise and decreases the live view focusing accuracy.
So this method should give maximum accuracy, although it all is dependent on not bumping or vibrating the lens when flipping the switch to manual focus after the first live view photograph is taken.
5DIII, 5DII, 7D x5, 6D, T2i, T3, 1D X, 10-22mm, 16-35mm II, 18-55mm II, 18-135mm IS x2, 70-200mm f/2.8L II, 24mm f/1.4L II, 50mm f/1.4, 50mm 1/1.8 II x2, 85mm f/1.8 x2, 100mm f/2 x2, 135mm f/2L x2, 200mm f/2.8L II x2, 1.4X III, 2.0X II, 60mm f/2.8 Macro, etc. only had room to list a few Canon items