Azimuth 2020

Civility? are you kidding me? Stupidity is more like it. Cleeds has no idea what he is talking about. He obviously flunked out of geometry in high school. I assume his talents lie elsewhere. At least I hope they lie elsewhere. As for sociopathology. Are we living on the same planet? You do not have to look very far to see some real sociopathology. Just open your door. And, the silent majority is just as bad. They should be chanting at the top of their lungs "all lives matter" not hiding in a corner. 
This is another post that is going to be deleted so you better read it fast. OK cleeds you can have it deleted it was really for your eyes only. Do yourself a favor and download a book on geometry and see if you can find an imagination while you are at it.

Bit hard to follow the conversation to know if any conclusions were reached:

Magnified, the grooves in a turntable may look straight, but they are still curved with the record which causes the cross-talk from one channel to be higher than the other with perfect azimuth. Stylus shape will impact this hence likely why high end cartridges will exhibit this more. Tuning azimuth based on averaging cross-talk will not be ideal. I do optically with a first surface mirror with a graticule, and if I am ambitious, I pull out the test record and do a high frequency sweep to make sure channels are matched.

With an offset tone-arm, usually the azimuth will change as the cartridge is raised and lowered, but the change will be very small over the likely height differences that would ever be encountered while playing, or what you put under the stylus while setting azimuth optically.  Note, I said "usually". For most tone-arms, the pivot angle is perpendicular to the main arm. For some tone-arms, the pivot angle is closer to perpendicular with the offset portion. For some, it is somewhere in the middle. If the pivot angle is perpendicular to the offset portion of the arm, the azimuth will not change as the cartridge is raised and lowered. VTA of course will always change as the cartridge moves up and down.

Robert, You wrote, "I pull out the test record and do a high frequency sweep to make sure channels are matched."
Matched for what?  Balance or crosstalk?

Matched for output level on a high frequency test sweep. If the azimuth is off, you will get left to right output level variations as the frequency changes at high frequencies.

Yes, but changing azimuth will also alter crosstalk, and azimuth has far less of an effect on channel balance vs crosstalk.  So a little change in balance makes a big change in crosstalk relationships.