Yep.
Also, it's easy to lose the context of how many people a parking lot actually means. Taking an average of 4 people a vehicle (for every couple there's a minivan), 5k spaces is 20,000 people. That's half a big park's capacity right there.
Throw in a third of the estimated 32,000 people (4 per room) available from their current resort offerings (including Endless Summer) - 10,000
Plus 2 thirds of the hypothetical 1,500 rooms opening with Site B - 2,000
You're at theoretical park capacity of 32,000 (closer to 35,000 in reality). Throw in bus drop offs and ride shares, it creeps higher.
That's... About right.
EDIT - Did I just figure out an unannounced park's capacity?