I don’t think I explained it very well.
Are you traveling after August? If so, there are no dates released yet, which is why it shows that message. At least, that what I believe is happening. I don’t think it’s related to the number of park reservations you can make.
It may be clearer if you choose the option without a hotel reservation.
If you’re travelling before September, then you maybe correct. But I was able to book park reservations for 25th & 26th August, which are the first two days of my trip. I can’t yet book anything later. So I have only 2 park reservations, which is not the AP limit.