DUBXH
Once the bridge is off the a/c, you must assume the door is armed (for chute deployment). If there's a fire outside then the crew in the a/c will be using all available chutes away from the side on fire for evacuation. I don't think they'd have time for the bridge to be re-docked, then go through the process to ensure that it's safe to open the door inside the jetty head. If the slide goes off into the bridge head, apart from blocking the means of escape, it might well kill the despatcher driving the bridge.
Of course, when the bridge is already docked on the a/c, then it does form part of the means of escape from the a/c. The hood is there to make a fire seal, not to keep the rain out!
Cheers,
The Odd One