Ambiguity will be the problem and it is solved by the rule of "not crossing at all". The lesser of 2 evils.
Maybe the problem here is that a 2 ton SUV shouldn't be driven at 50mph when pedestrians are anywhere near. I always find it interesting how the ones advocating for the absolute freedom of owning and driving an SUV everywhere, to carry 70kg of human flesh, are usually also the ones asking for the restriction of the freedom of other users of the public space.
Bad rules = ambiguous rules and need for interpretation and that leads to many bad consequences.
So, in the situation you describe, the solution is clear: the car has to slow down, and any police officer is supposed to notice that the car had to slow down and issue some citation to the pedestrian for not respecting the right of way. This is exactly how all traffic violations work: if some car is not yielding to you, you don't drive into them, you break to avoid the accident, and hope that the police sees this and issues a citation to the other driver.
If a bad rule is enacted and it kills 100 people per year more, will enforcement of the rule bring back those 100 people?
Rules should take into account the stupid things people will do and that in real life you won't get 100% compliance and enforcement won't get you to 100%. (many real life examples)
See a judge doing the right thing:
https://youtu.be/0PUgbArgXJA?si=9-8viC2MM-mIGEFe
We don't need a society that relies only on judges doing the right thing. We need better laws