The best understanding of those painted markings is that they mean nothing until you find strong social conventions indicating otherwise. City norms will be passed as state laws, creating discrepancies in rural regions between the law and the expectations. Bad drivers flow from everywhere to everywhere else with no regard for discrepancies in laws. The only markings I would trust are the scramble intersections, which I've only seen in Guam. And walk signals can often be trusted.

For evidence that people don't know state/local laws, ask a group of people in the US when they are permitted to u turn. It varies widely, mostly in insignificant ways.