That's very true. What I saw was:
6 slides opened max at any one time, with 3 staff watching them at the top and 2 at the bottom. Lots of whistle blowing when people stepped out of line.
I did see a couple of kids chancing their arm when staff back was turned and going down quickly together but would hardly put this down to staff supervision.
I can only go on what I observed and from my pov it was to the same standard, if not better, than those similar parks/pools in the UK