There isn’t really any signage at the end of the dead-end (there’s just a dead-end sign up the street), it’s just a round turnaround so you don’t get stuck having to back all the way up. I know one of the cars that parks there does it illegally because it’s next to a fire hydrant, but I’m not sure if the other ones are and just like you, I’m not making much progress on finding an answer…
this is at the end of 25th ave near chief sealth, and we get lots of cars that don’t realize it’s a dead-end until they turn down 25th ave.