We also lost about 0:40 on route choice to #10. I went the same way, except I didn't notice the unmapped road that you took, and was therefore surprised when the road I was on turned into a cul-de-sac (but with a right-of-way connecting out to the main road).
Yeah, I was thinking going right through the park edge, but seemed a bit more trail running and drop climb. So tempting to run on the road.
I looked at the unmapped road as I was running and noticed it connected with the next one over and figured it was just missed to put on the map.