It is a cheap non solution that allows leaders to say they did something without actually doing something that would require a sacrifice, such as money, or in the case, sacrificing the convenience of drivers who are presumably more politically powerfully than pedestrians.
The crosswalk buttons work, the traffic lights turn red, but that does not mean a driver will pay attention and check for pedestrians.
Right turns on red lights are allowed. As are left turns on greens, while the walk signal will simultaneously tell a person they can walk across the road. In both cases, the traffic light does not stop the driver, the driver has to be actively checking for a pedestrian.
All of this absurdity could be solved with a simple stop sign, but that would be a minor inconvenience to motorists.
The advantage of this is that it's pretty easy to detect cars by detection loops in the road, and if you detect them in time, the car doesn't even have to slow down. Unless there are too many of them; then they will sometimes have to wait for pedestrians to cross.
I don't quite understand what the flags in Bellevue are for. Are there no traffic lights? But then what are the crosswalk buttons for?