It appears you are correct. There is a number to call on the website. SFWMD.gov

If I recall correctly, they won't open 2023 reservations until late in the year, then all of 2023 opens. You may have the option of calling of reserving via email as well. I have had very fast and helpful response from emailing specialuselicense@sfwmd.gov

They have made changes after Covid.. 30 days in advance. Back on 2019 we were able to plan 8 month’s ahead and that made it so much more convenient.

I've stayed there often. Best to call and talk to someone at the park. I was able to reserve 8 months out easily with a phone call.