Today I drove on my neighborhood unmarked roads without FSD engaged, and I was looking at the visualization. As it turns out, several times when the car hovers to the center, the AP/FSD-ready icon (gray steering wheel) disappeared. So it's clearly confused whether it's driving on a single one-way giant lane, or if it's a road intended for 2-way traffic. Sometimes when the seam in the asphalt becomes more visible, it interprets that as a centerline marking, and the car dives over to the right, and the AP/FSD-ready icon reappears.
I am in IL and have this exact thing in my subdivision. I is a wide street intended for 2 way traffic, but FSD will stay centered, with the occasional yellow centerline popping up on the display and it getting over. Every time an oncoming car is headed for me, i give it lots of time to scoot over to the right but it does not very much at all and I have to disengage. One a related note, the entrance to our subdivision has an "island" that splits between the entrance and exit (left and right lanes). It has problems seeing this island when heading out of the subdivision and about 50% of the time will head right for the island instead of scooting over a few feet to exit the subdivision using the lane.