Never had a robin-hood myself, but I don't shoot all that much.

Keep in mind that just because you don't "robin hood" an arrow doesn't neccessarily mean youDIDN'T put that arrow back into the exact same spot as the previous arrow. Also keep in mind that just because someone "robin hoods" an arrow doesn't neccessarily mean theyDID put that arrow back into the exact same spot as the previous arrow.

When arrows hit the haybail they don't always stick in perfectly straight. Ever go to retrieve your arrows and notice one or two are stuck in a bit crooked? Many times right? Well, if you shoot off the knock of an arrow that stuck in crooked, you may be as far as a few inches off from the previous arrows exact point of impact.