Kinda sounds like the small engine instructor needs to go back to school...But of course I know of many small engine/lawn mower shops that have no knowledge of how the electrical systems even work. Just a major embarrassment to whole industry as they should know this in order to repair the equipment.
It doesn't matter if your in business of repair if you are repairing lawn equipment, vehicles, office equipment, or financial equipment. You must be able to repair both the mechanical, electrical, and electronics nowadays. When it the electrical and electronics you must understand how things are configured too.