If you honestly don't believe a zero cost title upgrade that gives a ship two atks a turn isn't a power boost I don't know what to tell you considering gunner is still one of the most popular upgrades in the game and costs 5 points for the privilege.
It isn't a zero-cost upgrade because it has the rather significant cost of preventing you from shooting out of arc with your turret weapons, weapons that have point costs and power levels balanced around the ability to shoot out of arc. So the A4 title itself costs zero points, but the real cost is the overpayment for the turret weapon.
And gunner isn't a very accurate comparison because gunner gives you another shot with your best attack, while the A4 title gives you a mediocre primary weapon attack that probably doesn't get any dice modification. Gunner costs more than the A4 title because its effect is a lot more powerful.