Not all aircraft of a particular type will have
exactly the same systems.
eg. whilst most GA aircraft have their DI 'powered' by suction there are quite a few electrically-driven ones installed.
"What's this extra pitot tube thing sticking out of the cabin wall on the Piper Arrow?". "No idea", is the normal reply. Then why are you flying it??
Golly.. is that system still been used ?.
(I thought it had been disabled years ago.)
"What does it mean (what can you say "for sure") if one of the little green lights doesn't come on when you select undercarriage down?"
How much detail do you want ?
Are you expecting your students to have an intimate knowledge of the entire electrical system and the undercarriage mechanicals ?
I'm more content to simply know what I can and should do if a fault manifests itself during flight.
Having said that, I do agree that some basic systems-knowledge is vital, even for non mechanically-minded aviators.