And they measure rainfall with a little cup. That doesn't mean it's not scientific.
The AFL have a policy. I presume they didn't just draw it up on the back of a coaster. I don't know, they could have I suppose.
But I would assume they consulted with people who know stuff about stuff like this, and I presume the AFLPA gave it the once over to make sure it took into account the well being of players. There's a reasonable chance that the AFL's insurance provider even signed off on it. The ground was built to meet that standard and it does.
I know they use the penetrometer to get a reading of race tracks and you can tell double check how well they called it based on the speed at which the horses run. It's a perfectly reasonably thing, calling it a metal spike as a way of ignoring it and then telling me that unamed players say they think it's a bit hard so the metal spike is wrong is nonsense.
The playing surfaces are actually the only thing we know meet a published standard of any kind.
We also know that the clubs have control over how much a player runs. If they thought it was too hard and they're pulling up sore, and we know that over running on a sore foot will lead to a fracture but the clubs keep running them anyway, how is that the fault of the ground. The ground was blamed after the fact. They should have seen it coming if it's so clearly the surface.
Normally you just put it down to bad luck. How scientific is that.