Keeping them small is fine as long as you arent stunting them to do it. If you know a snake is going to get 14+ ft and you try and underfeed it to keep it small, you dont need that snake. If you buy a snake that is going to get 14+ ft, then feed it correctly and expect an 14+ ft snake.
Not directing this at you personally but your quote seemed to fit my statement the best lol.