On, I see why these "explanations" confuse you. They totally omit the description of how PDAF actually works.I am interested in the general theory about on-sensor AFMA and its limitations, and how it will affect my photography. Here are some good articles of how PDAF actually works and on-sensor limitations: http://www.clarkvision.com/articles/understanding.autofocus/ and https://photo.stackexchange.com/que...ection-autofocus-need-adjustment-for-accuracy
(Maybe I should write one myself, but it would take a couple of hours of my life, so I'd rather avoid it)
They are affected in exactly the same way as the focus is affected.PD uses phases from opposite sides of the lens, and these may be affected by aberrations of the lens and differences in path length because of mechanical errors.
In Canon's DPAF, it is possible (and common) that pixel pairs receive non-equal exposure even when they are in focus (the main reason for it is that the EF lenses are not fully image-space telecentric, but tilted or shifted optical axis may also play a very small role). However, if the lens is in focus, there is no phase shift in the dual-pixel array, no matter where the lens optical axis is.
Only when the PDAF points are sparse. Not Canon's case.On-sensor PDAF requires contrast detection or its equivalent for final accuracy:
AFMA may be necessary for a multitude of reasons, but why do you think that adapter-introduced tilt is one of them?Read this to see how AFMA can still be necessary if you are not convinced: https://eduardolibby.com/2018/12/22/nikons-z7-requires-af-fine-tuning/ ("The claims that on-sensor phase-detection autofocus sensors in Nikon’s Z7 does away with autofocus fine-tuning are wrong. I had to use AF Fine Tuning to get my lenses to focus properly.")