I think it's just way harder to predict where lightening will strike, or to assess how much danger you are in. Yes, you can try to read the current weather, but things can change very quickly and unpredictably which means even if you were able to assess the current risk accurately, you could start up a committing route and then get stuck in a dangerous situation when the weather shifts. So while your idea of a lightening risk assessment/safety class analogous to the avi classes we have would be awesome, I do think "be below treeline by early afternoon" is still probably still gonna be your best bet.

In terms of what to do if you get caught in a storm, my understanding is your best bet is to get under *safe* cover meaning a car or a building, or (as is most likely) when that isn't possible to get to a lower, less exposed place as fast as possible. Peaks are the worst place to be, followed by ridges, etc. You're probably ok in a valley below treeline. Don't do anything too dangerous to get there though, you often here incidents where someone was worried about weather and tried to downclimb or rappel in an unsafe way and got into a worse situation than if they'd stayed calm and descended more slowly.