I couldn't have said it better. You'd think by now, people should be especially leery of editing photographs. No one likes being fooled. A normal system would auto-reopen the doors, and let the woman through. Now, in the case of the NYC subway system, it could be really old hardware.
Old hardware needs to be replaced.
This is dangerous. Someone could get pretty badly hurt in those doors if the train staff didn't notice and manually re-open the doors. The other option is that the administration decided that it would be more of a threat so people wouldn't keep rushing for the closing doors. This would ostensibly keep traffic and squeezing down. People are going to rush for the doors, whether they know it's not going to automatically re-open.