There was a big incident in Korea recently where some-one visited multiple parks and took videos of the women's changing room/toilets while pretending to text and play a game on their phone and then publishing online: http://themeparkreview.com/forum/viewtopic.php?p=1622144#p1622144
I hear as a result they have people patrol the changing rooms and toilets for people with phones, sadly a result of 1 bad person resulting in rules for every-one else.
I also suspect that the "no reentry after six" rule is probably to keep people from going out into the parking lot, getting drunk, and then coming back and getting belligerent or violent with scare actors, especially since the park is surrounded by rough cities and tends to have similarly rough clientele.