Fair enough although that's not the only statistics they cite.

More importantly I think they're trying to point out the converse of maybe what you're pointing to, which is that as porn availability increases, if it caused sexual assault, rates of the latter would go up. But it doesn't, you see the opposite trend time and time again.

This is one of those cases where you'll never be able to do a RCT, so any study will be flawed in some way (even RCTs have their issues).