I used to teach it as well to the students.
Along with no altimeter circuits as well.
If they wern't fixated on instruments I might not have bothered but almost all of the FS 1000hour pilots got those lessons. And nearly all of them were shocked to find they were more accurate on everything with no instruments than they were with them available.
How do you think instructors fly an approach?
I certainly don't sit there looking across at the parallax error. Set the machine up by ear and look out the window. And when the student is to fast or slow you tell them not by looking at the ASI but looking out the window. It annoys the hell out of them when your looking at the wing tip and saying airspeed low/high. Does the picture look right.