Considering that manufacturers literally stamp "CAL. 30-06 Springfield" or "CAL. XYZ Cartridge" on the barrels of guns since forever, it's understandable people use it that way. I don't sweat the small stuff and won't nitpick someone over it generally. However, the distinction becomes more important in the context of handloading and ballistics, especially handloading since you need a proper designation for every component and aspect to properly discuss it.
I don't get worked up over somone calling a detachable magazine a "clip" either. Context makes it clear what they mean. Good enough.
