Used to think that was just a dumb joke to mess with newbies. Then I saw a guy use a regular screwdriver in his left hand and strip every single screw head. Turns out some of them are ground for right hand pressure. Makes you wonder how many other simple things we get wrong.
My old foreman kept a left-handed screwdriver in his toolbox just to prove it existed. It was a regular flathead he'd reground the tip on at a weird angle. The joke was real, but the tool was just a messed up screwdriver.