Actually your butt has to be on the bench when you're executing the lift according to IPF standards but can be up during set up and IPF is pretty legit. I can't say what they are in the IPA, although it was on the bench when she lifted but not during her set up. You can see her drop her backside to rest on the bench. When it was up, her sternum was actually higher than the bar.
I don't much care for it myself and it appears freakish but how do you draw the line other than to say you don't like it.