From some searching around, it looks like the hole tilts as you stand on it. It doesn't look dramatic but it could definitely induce falls in people who are prone to such.

You'd think that, but they're required by law to post these signs since the... incident.

iirc that's what it said, but it was in regards to cave diving in a spring.

I'm guessing the windmill
and it resulting in more types of gruesome injuries than anyone would guess. Maybe even not just physical.