From the reasoning I was told this would make sense for either not to do this, but to answer your questoin this is for gate agents. "Once a customer is settled with belongings in an overhead bin they are not to be moved." I could not believe what I was hearing! This may not be the true policy and may be more of a local thing that has evolved at my station. Again, I follow the PMNW policy of going on board when time permits and upgrading before the door is closed.