It is an end of season event, the pool isn't open for non-dog related customers at all, its just the last couple of weekends where the temps are still just about warm enough, but there aren't really enough normal customers to make opening for them financially viable.
By having a couple of doggy weekends (with no other customers in between) they can make way more money which goes towards maintaining the pool.
If you'd read the thread or even skimmed through it... you'd know all that!