I can see how this can be very confusing. At the park reservation site I went through the reservation process for one of the handicapped accessible sites - the ones that are paved - and down at the bottom of the it says:
" * This site is reserved for visitors with disabilities. It can be reserved by visitors without disabilities only if no other site will accommodate the visitor's camping equipment."
Then farther down:
"Notes
This site is designed to meet the accessibility needs of persons with disabilities. If you do not require this type of campsite, please consider reserving an alternate campsite which is suitable for your camping equipment."
Better call before going to get an okay.