Not cool, and the "I agree" nonsense doesn't even give an option to explain the situation! I was a 100% load and ready to go but my system or your system failed somewhere and I got a bug splat that popped up in the background behind my load screen. I had to ctrl+alt del to find the damn thing since I locked up so bad!
That "I agree" thing is a one time only reminder that leaving games has a negative effect on other people. It's not an official warning against your account or anything, so don't worry about it.
The reason bug splats count, even though they are not your fault, is because there are ways to force a bug splat to happen. If bug splats didn't count toward leaving penalties people would abuse it and leave any game they want without punishment. It's not perfect this way, not by a long shot, but it's far better than the alternative.
