[NSFW} Why do we need two opposite concepts to describe one sex act?

I’m talking about oral sex given to a male. Some say he’s getting his cock sucked, while others call he’s getting it blown. Two diametrically opposite oral applications for one action. At least as far as I know, both words stand for the same action. If I am wrong on that, please enlighten me. If I’m right, then I am confused, so again please enlighten me.