It's all pretty arbitrary these days. They have guidelines here too, but most parents don't bother to adhere to them. Which yeah, it is their choice, but the problem is we have already determined that most parents don't always make the best decisions, so you end up having kids seeing content they have no facilities to comprehend. It sounds like you did your due diligence to make sure this would be appropriate which is admirable. I saw a double feature at a drive in when I was a young adult. One was Dante's Peak, and I think the other was Twister or Volcano.
Natural disaster junkie?
The guidelines are fine, but they are Guidelines. If with the parents, the parents decide. If Smallsteps was trying to go by herself or a group of friends, that is different.
I think a lot of times they don't even check anymore. Either that, or you can buy your tickets online ahead of time, so if the parent buys it for you, they don't even know what age you are. Yeah, it must have been some kind of theme night or something.