I am very sorry for my late reply Peco !
Those videos is max 1.5 min polishing and just a demo of a finish they make.
There is no such thing scratch free surface, to make scratches less visible you need to get them all in even direction, like Shigefusa dose.
If you twist Shigefusa knife in the light then you will see that scratches is much bigger then you expecting
So if you use more then 1.5 min on etch stone you will get better result
And as other said in that thread the harder stone bring up those scratches from previous stones and make them more visible, so you need to use more time on Harder Jnats
Those videos was just to get idea how stones work, speed and finish. I did not try to get perfect finish for that demo