The problem with making this jailable (which I do not support in the absence of a collision) is that you stopping to let a pedestrian legally cross is difficult to distinguish from you stopping in a travel lane or bike lane to pick up an Uber fare or stopping to double park near someone waiting for their own Uber. The latter two cases are actually obstacles created by anti-social behavior and are probably more common in aggregate than drivers stopping for pedestrians.
GP is suggesting they’re in a locale where mid-block pedestrians have the right of way. (I think they may have edited their post to add “at a legal crosswalk” as I don’t think I read that the first time and it does change the meaning significantly.)
Fundamentally the issue is that cars are huge visibility blockers. It is completely inconceivable that a cyclist could stop or slow to let a pedestrian cross, and the driver behind them would not see the pedestrian.
Without clear sight lines, drivers would need to communicate. But fundamentally drivers have extremely limited means of communicating information to those around them, and all of them are ambiguous. Hazard lights can mean a million things, including either "please pass me" or "it is extremely dangerous to pass me". In my city they most commonly mean "I want to park in this bike lane." Honking can mean a million things too, and sounds angry, aggressive, and startling. You can't really use your words, in a car, unless all of you have quiet engines, quiet tires, and roll your windows down. It is very hard, in most lighting conditions, to see the driver if they are trying to signal with their hands, because of sun glare, window tinting, lighting differentials between the cabin and the exterior.
So, the car in front blocks your ability to receive information about what's in front of them, while also being unable to communicate any helpful information themselves.
It's very easy to distinguish. People indicating to the right and slowing down are probably picking up or dropping off a pedestrian. If they aren't indicating, you must assume there's a hazard in front of them, slow down, and proceed with caution.
