Make of this sign what you will, but to me it looks like you get 4 hours of free parking and that restrictions end after 8pm. In other words, as long as you arrive after 4pm, what's the problem?
Yes, there are gates on the car park, and no they are never used. Anyone who'd been for a late-night KFC will be able to testify to that. Nandos is another place open to 10pm. The Gym at One Stop is open through the night from 8pm to 12am. So the car park has to stay open to allow for customers to access these businesses.
Still, there's no commercial link-up any more so it won't be promoted. Cut off noses and spited faces spring to mind.