Dash Oil and Brake Warning light - how are they triggered in the start function?

I think the simplest answer for OP, regardless of all this, is that with the key in RUN, the oil light and brake light work normally. There's no self-test for BRAKES like on later vehicles (that I'm aware of), and the default operation for the oil light also coincidentally serves as a self test. If hop in, insert the key, turn your key to RUN, and the oil light isn't on, something is wrong. (or you have an accumulator that hasn't bled down yet.)

You're not going to be driving with the key in START or ACC, so those don't really matter. There was another poster here that recently had the oil light on with the key removed, and that's a whole 'nother issue.

In my personal case, any bright ideas I have don't appear above my head as an Edison lightbulb or even an LED. At best it's an oil light letting me know I'm not as ready to go as I think I am, and in the worst case, it's a BRAKES light letting me know I'm about to hit a Chestnut tree.