why micro focus adjustment ?

You're right. It's not a specifically Sony Alpha AF problem, it's simply that AF is inherently subject to calibration problems, plus some lenses have focus planes & behaviour that make a simple definition of  "correct focus" impossible.

The higher end Alphas tend to have more sophisticated better performing AF. They also tend to have more sophisticated manual focus aids. MA helps AF to get better focus, but it can't solve all the AF problems, especially for zoom lenses.

If you want the sharpest possible images then you must learn when you can trust AF & when you can't. Individual cameras & lenses vary enough that you must do this by experiment for your camera & your lenses. Sony Alphas are rather good at giving you facilities to make this easier.

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Chris Malcolm