Oh no, most definitely believe him. You can certainly see the difference between 7200 and 6500 on different iOS devices. It’s neat to have it backed up by testing as well.
But then when I went on to ask him, that inspite of what he says about the white point calibration brought down to D6500 how is it that I still see a lot of devices almost all in the Apple Store to be still having the same Bluish-White displays and he did not have any answer on that ??