Covering instruments? Not in any flight manual, so clearly a dangerous maverick act
In all seriousness, I think it is a good exercise and my one unintentional no-ASI episode was when part of the pitot plumbing in C172 fell apart on the first take-off after its periodic.
Judging from the problems I sometimes see in pilots keeping the aeroplane in balance, some demonstration of 'butt calibration' might be good too!
With the technical skills addressed, I don't know how you quickly gauge the judgement side of things. But I've normally formed an opinion by the time we reach the run-up bay. That opinion is more than half of my answer to Pace's question re family members.