So:
1) Had our victim never been in prison with the perpetrators, and he was too smart to say , “No, you have me mixed up with someone else. Go ahead and rob me.”?
2) Had our victim been in prison but not recognized the perpetrator? “Sure, I…remember…you…yeah, you look…familiar. No you don’t need to rob me. Sure no hard feelings.” And therefore been unable to identify his assailant to police. Light may have been poor after all.
3) Had he known the perpetrator for who he was, but felt the need to report a crime in order not to violate his own parole? And then been too polite under the circumstances to identify his buddy.
4) Did he mention the prison angle to police? It got into the news story so one presumes he did.

Lots of intriguing possibilities.