K-1, 14 months, 20000 photos (gets a bit nitpicky)

The differenc e in PDAF anf CDAF is that with PDAF tHe af system can have one look at rhe AF senor to find out how much to move the focus and in which direction.

Yup. So knowing how the lens behaves is much more important.

With CDAF it does not know any of these things. So CDAF need costant polling on AF to first see if focus is getting better or worse. Once it confirmed focus is improving it know it is moving in right direction, but it still do not know ihow much it need to move. So it need to keep pollong AF until the focus get worse again and then it know it has passed best focus.

So with PDAF there is a handful commands and replys between camera and lens before focus is locked, but with CDAF there might behundreds. With PDAF it may always be a fixed number of commands, but with CDAF if will vary depending on how much the focus need to move.

Yup, I know that. And you could argue that this last ("Oh it is getting softer again, must backtrack a bit." is lens-dependent, but that is not required.
I mean, I don't know what the camera does. If it remembers the last 5 focus pollings, it could interpolate the right focus position. I'm assuming the screw drive shaft has some type of encoder on it. The step size could be reduced when the lens hones in and so on and so forth.
Not sure if such info is available.

Also, some motors designed for PDAF are worce when used for CDAF than others.

Sure.

And longer focal length lenses has heavier lens element to move wich can make it worse with CDAF.

Well, if you have a long lens that uses rear focusing (as most modern long lenses do since PDAF times) then that will not be more mass than for a 50...85mm lens that uses extension focus.

Mirrorless lenses designed for CDAF often focus by moving a small and light lens in the rear of the lens for best CDAF performance, while DSLR lenses designed for PDAF usually move a larger and heavier lens in the front of the lens.

But optimisation (=reduction) of the moving mass during focus has long been a design goal since way before CDAF.