Sorry if I'm coming across as presumptuous or something, it's just surprising to find that modern hard drives are still using the same basic mechanism that I saw inside the washing machine-size drives my dad worked on 40 something years ago, that would almost walk themselves out of their mounts thrashing their giant head servos around.

What you and others are describing is strikes me the way that opening up the package of a modern memory chip and finding a fabric of millions of tiny magnetic cores would, rather than a silicon array of capacitor/transistor cells - that for some reason no fundamental rethinking of the problem has prevailed and thus the only developments in RAM for almost half a century is miniaturization of what was being done in the 1960's.

The first PC HDDs used stepper motors and absolute positioning with cylinder geometry, just like floppy drives. Then they moved to voice coils and remote encoders (e.g. early Quantum drives), dedicated servo surface (drives with this report an odd number of heads), and finally embedded servo with non-cylinder-based layouts where each surface can have different track pitches and sectors per track.

I wouldn't call that "the same basic mechanism" as there have been lots of refinement over the years, but it turns out that having the heads themselves find what they need to read was the best solution.