That one is a rectangle inside a rectangle. The one in the OP looks like a capsule shape inside a rectangle, more like a usbc connector, so i assumed it was an intentional add by the the person who made the thing as another layer on top of the joke.

But yeah it could also be just someone trying to be clever while whining about usbc not being adopted by iphones sooner, and the icon is off because it’s designed to be made with 3d printer without a high enough level of precision