Fast-switching in CS:GO doesn’t speed anything up. It’s where you flick to another weapon then back again to try and speed up certain actions, like reloading. I played these clips at 10% speed to reduce my reaction times as much as possible. Between shots, a perfectly timed switch makes no difference though the chances are you won’t do it perfectly every time, so you’re really just putting yourself at a disadvantage. The reload animation is definitely shorter if you switch the moment the guy taps the magazine, but you still can’t fire for a while, as if there’s an invisible reload timer to stop people from doing this. So yes. In a best-case scenario it won’t make any difference, and at worst you’ll muck it all up and not reload, or will take longer to do so.

Get out of the habit, it worked for Source but CS:GO has it sussed. Or should I say… SOURCED! AHAHAHAA.

As found on Youtube