I agree. While elevator etiquette (and logic!) says that people who are getting off should go before people getting on, if one is getting off the elevator, it's expected that you will be a) near the door or b) moving toward the exit when the doors open or c) (when it's really crowded and you got pushed to the back) saying "excuse me, please, this is my floor" while attempting to move toward the exit.
People who are standing against the rear wall when the door opens and not moving toward the door are giving a very clear "I intend to continue to another floor" signal. I don't think it's necessary to ask a person who is standing in that manner when the doors open, because 99.44% of elevator riders know that they need to move toward the open door or verbally communicate if there's some reason they need an extra moment when exiting the elevator. Moving toward the back is the appropriate thing to do when you intend to keep riding and others are going to get on.