I doubt the bar is particularly high and the onus is on the city to create signs/paint curbs to indicate if it's longer or shorter.
As it stands, if there's a red curb or parking prohibition sign already next to a crosswalk, it dictates distance - whether longer or shorter - and there are a lot of intersections with those already that are much shorter than 20 feet - like where fire hydrants often are. If SF doesn't repaint/resign those, then nothing happens.
It's only for unpainted/unsigned areas where the 20 ft rule comes into place.
OK, I see that now:
But honestly I often see cars stopped (waiting, not parked) in red zones and have never seen them get a ticket or even asked to move on.> And the law actually states that local authorities can come up with their own distance rules instead.
I didn't know this!
I wonder whether (n)(1)(B)(i) is, in practice, a high bar.