My bridge arm is slightly bent.
Observations I have noticed:
1) Those that shoot with bridge arm locked, tend to do so because:
1-A) They hold the cue too far back with grip arm.
1-B) They tend to have too long a stroke.
1-C) They stand too straight with the cue.
Now, most of these tendencies can result in weaknesses in your game.
A 45 degree angle is recommended in relation to your cue. People that stand too straight will put their hip close to their stroke, among other things. It's like shooting a rifle from a standing postion with both feet together instead of spread apart with one foot in front. People with too long a stroke will not be consistent throughout all of their shots they have, yes, I will make an exception for the Filapinos. And people that hold their cue too far back with the grip arm are not stroking the cue, they are pushing it.