If you’ve ever almost walked into one the failure case is really clear. They use stopping as a default mitigation strategy when something unpredictable happens - this isn’t always a good solution especially when suddenly blocking transit (Crosswalks, bike paths, railways, traffic) instead of just crossing it. This is a failure case humans can get cited for - I hit a car in the bike lane once when they did a left turn in front of me and it was legally the driver’s fault for blocking that path.

It is just another characteristic they need to figure out in a complex problem.