It often does, and it also often avoids doing so. And there is a debate within the legal community about which approach is better.

See https://en.wikipedia.org/wiki/Bright-line_rule for a starting place to learn more about this.

Sure, but if you get pulled over while doing so the "Law" will be well within it's right to issue you a ticket despite your protestations of fuzzy gray areas. The law is quite clear here the fuzziness is purely in the discretion we grant enforcers of that law.

I wasn't drawing a distinction between the law as written and the law as enforced, because the latter is the one that matters in a practical sense. So sure, if you make that distinction, my comment doesn't make much sense.

The discretion police use is a huge gray area that is often problematic, but probably less problematic than not having a gray area.