Other mistake: At the beginning of the movie the bomb is revealed to have 58 seconds left, but actually explodes after about 68 seconds. (00:02:40 - 00:03:50)
Other mistake: As the girls learn about their assignment from Charlie, he shows them a film. The film shows Knox in a tree. His sweatshirt says "BOSTON" in white letters. It is backwards in that shot, and the scene following. (00:13:34)
Other mistake: At one stage the Angels speak with each other in a different language, so that the people sitting next to them wouldn't understand. Having listened to it for a few times, I realized it was Finnish. Funny though, the thing they actually said there (in Finnish), was totally different than the written translation. (00:41:45)
Other mistake: When the agency blows up, the girls are thrown backwards by the blast you can see big pieces of debris flying outwards. However, NOTHING falls on the girls...you'd think that they would get hit by some of the debris, right? (00:58:45)
Other mistake: During the five man fight sequence with Drew, she does a split kick in the air and "kicks" two guys, but her foot is clearly a good distance away from even grazing the guy on the right anywhere on his body. (01:16:45)
Other mistake: When Knox shoots at Dylan/the glass, if you look closely, you can see the first shot hits the glass just past the left side of her head (on the viewer's right) but when they slow mo it down, suddenly the bullet is on the left side and shoots the glass just above her right shoulder as she propels herself back.
Chosen answer: I suspect that like much in this movie, it was merely conceived to be an 'exciting' opening for the movie and logic played little part in its inclusion.