Why is it in Hollywood movies every time there is a vent or AC unit someone has fixed little ribbons on it? Is that a thing americans do? Why? The vent in this movie is close to the floor in the toilets of a train. This implies someone got on all fours ON THE FLOOR OF A TRAIN’S BATHROOM to stick those ribbons there for a reason i can’t even begin to comprehend.
Whether the air is blowing or not is strictly irrelevant to this scene. something has been hidden inside the vent which the protagonist is about to find out when the picture was taken. We will never come back to this bathroom later. As a matter of fact it would have made sense if the ribbons were not floating and the object was big enough to obstruct the vent, but this is not the case here.
In that case you’re right and it’s just bad cinema.