I doubt this is by design, but just a matter of the way typical wipers work.
The wiper motor assembly has a switch or sensor to knows when the wipers are parked, or at their down, unused position. This has been the case for decades. This is so that when you tun them off, it maintains the circuit or power to the motor until they are parked so they don't just stop in the middle of the windshield.
I imagine that when you pull the stalk to spray fluid, it simply engages the motor assuming it will get to the point where the auto park sensor determines it needs to keep it going until the park position. If you flick it too fast, it doesn't have time to engage to that point so it never does a sweep.