This is an excellent article on how much of our (American) culture is based on what we’re used to and consider universal by extension. Which I suppose is true of every culture, but in this case it’s not just about gender roles, but cultural interests.
Basically, the argument is that “throws like a girl” applies pretty well to most European, Asian, and every-other-place-in-the-world men. Because they don’t play a throwing sport growing up, they play a kicking sport. It’s not some amazing talent, it’s a learned skill. Sure, there is talent for being extraordinary at throwing, but that’s not what “throws like a girl” is referring to. It’s not “can’t exhibit above normal throwing skill,” it means “lacks the basic ability to throw like a competent human being”.
This, of course, presumes that girls are not really human beings, at least not when it comes to throwing. Nor are Europeans, South Americans, Asians other than Japanese and Taiwanese people, etc.
So, the much more accurate “throws like a t-rex” is proposed. It not only doesn’t make unfounded gendered assumptions that also apply to most people in the world, it also better describes the actions that lead to poor throwing. Arms held close to the body, not much shoulder rotation, excessive body movement. It applies better. Let’s make it a thing.