Well, typically in games with this kind of sentry companion (particularly Gradius, hence the "Option" comparison) you get to press a button to switch around how these things align themselves with the player. One formation might swirl around the player in orbit, one might fan out behind the player and stick to his back, one might follow the player in a line pattern, and so on. No reason one mode couldn't be an "autonomous formation, fire at will" if insisted upon.
I personally prefer the "fire when player presses an attack button/makes an attack" mode, maybe someone else would take an autonomous mode.
If it turns out making it fire in "the same general direction" makes it miss too often (which frankly I think also has its uses via general suppressive fire, bats where you sort of miss anyone? Or more giant enemies where you don't need pinpoint accuracy and can bombard them with multiple shots?), either let the player tighten the sentry formation so they don't have too wide a spread or make them hew closer to your firing cursor in general.