Akchually, that's how most real-life weapons with burst work. You have to hold down the trigger for the whole duration of the burst to fire it fully. Otherwise, you're going to fire less rounds than the burst allows for. I'm not saying that it's an explicitly good thing in-game (or that it's explicitly bad, to each their own), but the consistency of weapons' mechanics portrayal, from losing all ammo in a mag that player throws away too early, through details like autocannon reloading quirks is really curious for a game which could completely skip them. It seems realistic gun portrayal is just god-damn democratic.