I also find it very discouraging that you have an instructor that could not explain why a check was being conducted. This is simply unacceptable. He/She should be able to explain exactly why every check is being preformed and what would be examples of an anomalous outcome.
A very good point. I try to have what I consider a rational explanation for every item on the checks I teach my students. BUT... what if, despite the apparent rationality of what I am teaching, it's WRONG? There's plenty of generic stuff we teach
a) mag check after start to make sure they're both working, mag check on shutdown to make sure they both ground
b) select 1200 rpm when stationary to prevent plug fouling
c) after landing checks - shed electrical load to refresh the battery before shutdown
None of these appear in most POH but have crept into published checklists. Some people have suggested that these 'bloated' checklists full of bullsh*t are there simply to delay departure so schools can make money - also rubbish. They are produced by well-meaning folk who want pilots to operate aircraft safely.
More received wisdom - the left tank vent on Cessna 100 series a/c is 'hidden' behind the strut in relatively stagnant air to reduce the over-pressure in the tank compared with the right.
TOO