I have actually done these. I don't remember feeling much in my chest or triceps, I remember them really torching my front delts more than anything else.
Yes used in boxing training but most use a medicine ball back in the day.
Infact I first did these back in '85 with a medicine ball in basic training ( boot camp )
The PTI was called Harry the Bastard.
He loved to beast us with the medicine balls.
Infact holding it out at arms length he said , you love my medicine balls don't you.
I laughed out loud & got a bad beasting 🤣
When we finished we got him a pewter beer tankard with " Harry the Bastard" engraved on it.
He loved it & came to our room with a slab of 🍺 and we toasted his new beer tankard..