I doubt pivot tightness has much to do with it. My Centofante 3 blade swings freely if I depress the lock, so there is extremely little pressure from a pivot standpoint. I have always maintained that lockbacks just aren't conducive to flicking open due to the reason Evil D mentions above: the lock is constantly applying quite a bit of pressure, making flicks difficult. I'm not a very good flicker (I find no entertainment value in flicking and prefer to open my knives in a controlled manner - not that there's anything wrong with those that do flick
), so maybe I'm just not skilled at it, but I can usually flick most my liner/integral lock knives if I give them a try or two. I can't say the same for any of my lockbacks, including the Centofante.