If I have an image and I want to print 2 copies, I get one sheet of paper printed both sides with a duplicated image. I guess 99.999999% of people when they print 2 copies of an image would like 2 sheets of paper, with one image each.
I think this is an annoying bug. I wanted to print 20 copies of a birthday invitation. I ended up invoking 20 times the rater unresponsive and very slow print dialog.
Not a bug, the problem is that double-sided printing might have been left on from a previous print job and not disabled.
The reason Jumpenjax’s answer is good is that double-sided printing is a feature controlled by the printer driver software, usually not by specific applications like Photoshop. In any application, I am in the habit of checking all print options before clicking Print, in case something is not set correctly.