Not bad. Less good.Someone has to explain to me why 'flat' break is bad.
If we can all agree that when we're talking about this movement, we acknowledge that every pitch moves, and this is "extra" break/movement. The kind that tricks the batter (as opposed to a normal "straight fastball" which has some vertical movement, and probably some horizontal movement, that's easier to read).
A ball moving in one direction (horizontally) is easier to adjust to than one moving two directions (horizontally and vertically).
Not just that, but between horizontal and vertical movement, vertical is better because a batter whose bat is on plane can still hit a pitch with horizontal movement even if they're fooled by the break. Not so with vertical. Or at least not as easily. All of this is in degrees with no absolutes.