Once more for hyper-technical amongst us... a Glock Model 22 is only produced in caliber 40 S&W, but most people don't know a Model 17 from 19 from a 22. I'm sure there are lot's of people who would think your Glock 22 was a .22 caliber pistol. When someone says they have a Glock 40 they are referring to the Glock Model 22 in most cases.
Yes, inadvertant firing of most modern pistols is a purposeful act, but not an intentional act. Yes, some cop's finger did pull the trigger, but they pulled it unintentionally. Now why did this happen? Why was the finger on the trigger of the cop did not intend to shoot? You have to take into account the physiology of entering into a hostile situation. This is a far cry different from standing on a firing line at a range. If you're drawing your weapon in the former there's a good chance that you'll be shooting, but also a good chance you won't be, and there's usually little or no time to decide which way you're going to go.
On a range you have all the time you want to get situated and then only let your finger enter the guard when you are actually ready to fire. That's a luxury that's absent in a crisis, which is why about 99.9% of the time you'll be drawing your pistol with your finger on the trigger even if you're not actually ready to shoot. And in most cases, if applicable, you're drawing your gun with your index on the trigger and your thumb on the safety, which provides you with an extra layer of security against unintentional discharge. With a Glock you don't have that safeguard, hence the huge numbers of unintentional discharge reports as compared to pistols with thumb safties, DAO pistols, or revolvers.