Sure - but that's true of any crimps and any tool.Well, they would be a lot worse if they were not the exact size for the wire being crimped and vice versa.
As I always say, from my very non-expert position,I've never been particularly comfortable with them - but who am I to know, given how widely used they are?!So, are butt-crimps not a good idea in the first place?
Kind Regards, John