... then through optical viewfinder is just using the human judgement (and human speed of operation) in PDAF, same principle ... so probably both manual focusing techniques shall be included
I think Doug Herr (telyt) is right, that the focus detection we use in manual focus is basically detecting contrast, not detecting phase differences. (Unless you still have a split-image rangefinder style VF in your SLR.)
Some differences in MF between using the reflex mechanism and focusing screen of an SLR vs using the live preview of an eye-level EVF or rear screen:
- the reflex system suffers from possible misalignment of the mirrors and focusing screen relative to the sensor (as seen in the inaccuracy of SLR PDAF in the tests, improved by calibrating for the lens-body combination)
- the image in the OVF is of lower resolution and smaller than is possible with an enlarged live preview
- the image in the OVF is somewhat more detailed than with an unenlarged live preview, and also far larger than an unenlarged rear screen preview.
Using enlarged preview might not be possible with some moving subjects, adding one more reason why moving subjects are the last bastion of advantage for optical reflex viewfinders.