In post #42 you said that was your last comment on this subject, yet here you are.What the hell!
Quick calculation:
Volume= original volume (at 1 atmosphere,or your elevation)*(original volume/final pressure)
Zero volume would be impossible to obtain without a vacuum chamber due to the inability to hold a seal! However actual volume of O2 in both nitrogen vs air fill. At the pressure of inflation,using the formula above you can determine the actual volume of O2 in the tire.
No place that offers the service to my knowledge considers the volume at elevation pressure.
Furthermore, over time the O2 will escape the tire,just as the physics used to remove the O2 in their equipment does. You may ask if the tires will do the job anyhow, why bother? Well because the process of adding air will keep the O2 in abundant supply.
On the same principle, topping off the pressure with nitrogen, will continue to reduce any O2 that was in the volume of air during the original tire installation.
There comes a time that everything becomes foolishness, when carried beyond reason!!!
Have a good evening, and don't lose to much sleep over this!!!
Carry on.