This is for contrast detection which is used by older/cheaper detectors, and specifically not in the iPhone 6, Galaxy S5. Contrast detection is why my iPad (4th generation) can be seen to visibly scan through its whole focus range before fixing focus on the part I want in focus. The whole idea of phase detection is that this is not necessary with the correct hardware.
Indeed, the submission itself is phase detection. That comment was the contrast detection for, humorously, contrast.
Though the iPhone 6 and other devices still feature contrast detection (which is generally a function of the image processor) in addition to phase detection. They each have strengths and applications.
This is of relevance given the phase detection offered on the iPhone 6 (and previously released on the Galaxy S5).