[William Sommerwerck]

The automatic adjustment looks at phase difference between
the channels and drives a motor which adjusts the head.

Actually, that isn't the way it works. As the phase between the channels of
a stereo recording has no necessary standard or fixed relationship, it's not
a useful way to set azimuth.

In the Nakamichi, the outermost track (the one closest to the tape edge) is
split into two head gaps, each with its own amplification. The head block is
moved until the HF output of these heads peaks. (Or is it that the phase
difference is minimized?) Anyhow...