It does, just try shooting a gv with them at 1K+. A manned ack will hit the exact same spot every time, the ostwind will miss from time to time.
Yup, that's the 'shaking' effect I referred to that they added presumably to simulate the fact that it is firing from a mobile chassis. But, the maximum dispersion is less than the diameter of a fighter at 2k in full profile aspect so really doesn't have any net detrimental effect on aiming. If you're shooting at a fighter beyond 2k you're hoping and praying anyway so the dispersion is just as likely to randomly help you to hit as miss.
The only time it really makes a difference is if you're shooting at bombers beyond 3k where the extrapolation of the dispersion at that distance can cause you to miss occasionally. But, when your lobbing rounds up at overflying bombers you have time, on an average pass, to put up 20-30 rounds, so again it's all going to average out. The higher rate of fire more than makes up for the almost negligible dispersion with the notable exception of shooting at other ground vehicles where pinpoint accuracy is required to hit a stationary target in specific areas..But, that's not really what the Ostwind is for...

The 'shaking' effect was much, much worse when originally implemented. The dispersion was greater than the diameter of a fighter at 1k which made the Ostwind almost useless. Thankfully, HTC realized their error and quickly reduced the shaking effect to what we have now. It is mildly nauseating but has no real effect on the Ostwind's effectiveness vs. aircraft..It is entirely possible the 'shaking' effect was added specifically to hinder it's usefullness against GV's, it was somewhat unbalancing without it. An Ostwind could disable a panzer more quickly and efficiently than another panzer could even at relatively long distance.