Arrived just after opening to beat any crowd. Wanted to walk around with my kids to burn time for 30-40 minutes. Parked in a half empty parking lot, 4-5 cars and was approached and told we could not visit without a reservation due to the parking.
Our baby needed to breastfeed so we waited for mom in the parking lot for 5 minutes or so and were approached again saying that in addition to the parking problem (which was visibly not an issue at the time) the owner had closed to walk ins that day due to weather. It was a little windy but otherwise the nicest day of our trip (sun out, no rain etc)
It says reservations are highly recommended on the website (due to limited parking). If they are required, then say they are required.
Driving out we noticed that the lower staff parking lot was entirely empty. I presume that means some of those 4-5 cars were staff.
We had good time at tunnels beach which is beautiful. Because we were so early, that parking lot was empty too.