Haven't heard about it. I breathe with the "proper method" instinctively and never knew this was even a thing.

Perhaps it's something specific to American culture.

Cartoons always show chest breathing.

No it isn’t true most kids in India are taught to breathe through stomach not chest.

Watch any lessons in pranayama you will know it’s part of daily routine taught to many Indians and now most yoga practitioners learn it.

Gym class as a kid? Sports teams during high school (Running, Wrestling, Soccer, Football, Baseball, Lacrosse, etc)? Meditation practice?

I was taught that we learned bad breathing technique through learning how to speak. I don't really know how accurate that is, but non-speaking babies do proper breathing, and speaking age children no longer do for the most part, so there is correlation at the very least. It's anecdotal at best, but I didn't see anyone mentioning the speech aspect.

I've heard this in a variety of meditation & martial arts communities. I think it's is more of a straw man that various groups use to build up the importance of their own methods.

Definitely new to me.