Yes, that's one specific hypothetical, and it would probably compromise the case. But there are several other possible hypotheticals, such as:
"You ID'd Harmon as the KU player sitting next to the man who assaulted you, but Harmon played for Illinois."
1. "No, I initially recognized a KU player sitting next to him, then when I saw the picture with Harmon, I recognized that Harmon was the other person sitting next to him.
Or 2. "I initially thought the guy sitting next to him looked like a KU player, but I admit I don't watch that much KU basketball. When I saw the picture, I realized it was definitely Harmon who I had seen next to him, and if he played for Illinois, I clearly don't know the KU roster that well.
Or 3. "Yeah, I'm not that confident in who I saw next to Terrence because I was so focused on him the whole time from when he called me over until I was right there next to him. I caught a glimpse of the people around him, and they all looked like basketball players, and the guy next to him looked like a KU player I think I've seen on TV, but I didn't really look at him that closely since I was so enamored with Terrence. When I saw the picture with Harmon, he looked like the guy next to Terrence at the bar who I thought played for KU, but I know I can't be 100% sure since I was looking at Terrence the whole time. (And suppose the prosecution can show that Morris wasn't wearing a yellow shirt that night)
I'm just saying it's premature to judge the case based on hypotheticals we don't know (yet).