I have no idea where the photo originally came from. I missed it if it was posted a few years back.
I agree, the photo probably doesn't have anything to do with the drawing.
Looks like someone wanted to make it easy to run several conduits together, and someone else noticed the similarity to revision clouds.
On second thought, the hole might even be for a HVAC duct. There's no way to know which trade cut it. It might even be legal if its in a shaft wall chase.