If individual muscles are take off the bone before going into rigor, or after going into rigor but before leaving it, they can contract or stay contracted. This makes them tougher, and aging won't help. A similar thing happens when meat freezes before or during rigor.
Mule Deer, I believe that is exactly what my friend said, that is the part about the
muscles contracting and staying that way would make the meat tough. His view was if you were going to bone one out to wait a day or so before doing so.
