I can't quite agree with the upper arm being 90° to the torso thing. I know it's well accepted, but that leaves out the lower arm angle to the upper arm. The more straight the two are in relation to each other the more forces from bumps and jolts will be concentrated on the shoulder and the hands. Maybe some to be felt by the elbow too.
So to me, some might still have the reach for their bike wrong, but think it correct because they only look at that one criteria of 90° upper arm to torso.