One of those counties is Rockland, which is in NY. I wonder if it's counting bordering counties for states, since the assumption may be that the closest essential services for some Rockland residents may be in New Jersey.

Ah! This looks like a bug with cross-border calculations. Ideally it would not show a Rockland County, NJ - it might cross state borders to perform calculations but they should all have a 'home state' that matches to the right county. Thanks for the example case, I'll work on a fix

I know at least in Rockland's case, their power utility extends slightly into NJ. Can see it on statewide power outage trackers like this one: https://projects.nj.com/data/outagetracker/