You still get a full flash duration even when you weren't looking directly at the flash, imagine a scenerio that a flash is about to pop in front of you, so you turn right by 90 degrees, and the flash isn't in your screen anymore, but you still get flashed like you were looking directly at it.

In CSGO, when you can't turn 180 degrees but only 90 degrees, the flash is much less effective and takes a smaller amount of time to clear away. But you still get kinda flashed, you need to have your back completely turned to the flash to have it not effect you at all, so you can kinda turn enough so that the flash is out of your screen, and get effected by the flash just a little. Which is a nice thing because you're not always in a position where you can fully turn your back. In VALORANT, this is non-existent