Should I preheat a pan, or start the cooking timer immediately?
If you cook (or bake) using a timer, you should always use preheated equipment.  Your stove top may differ from my stove top in terms of the length of time it would take to get to high heat (hell, my stove top wouldn't even hit high heat in three minutes), and this would greatly effect the final quality.

Always preheat, the instructions expect it.  Otherwise, it would tell you to put a pan on the stove top, place in pan, and turn on to high heat.  Leave for three minutes and remove.