As far as I understand the ICAO guidelines, the “X” across a helipad signals to third parties that they can’t land there
That helipad with the X on it was the old hangar pad when Seaworld Aviation had the Longrangers. There were/are helipads on tracks that would slide in and out of the hangar. Was easy back when they had 206Ls. Dont think they use it anymore since PHS took over the operation and use the AS350/EC130s - prob why they put an X on it. Also in the old days a lot of the TV station machines would drop in and say hi and land on that pad, presume thats why it now has an X on it because totally different operation running things and they have all the four new pads.
The other pad that the accident aircraft took off from is right beside the ticket booth so lot of machines come and go from that pad. Its an ease of convenience for those inside the park who have bought tickets, buy ticket - walk 20ft to the helicopter and take off rather than having to go outside the park and then over to the new facility.