I’m an Engineer who has testified as an expert witness a few times. Knowing how attorneys often operate during pre-testimony interviews, there's a good chance Joe’s pre-GJ interview went something like this. I know this is just speculation, but I think its very reasonable based on what we know about the tactics of the investigators and the OAG and what we know about what actually happened in the shower from Allan Myers, and the fact the the GJ testimony was apparently the first time Joe ever used the terms fondling or sexual nature with regards to the case.
Investigator: Joe, Mike says he told you he saw Sandusky raping a boy. Do you remember that?
Joe: I can’t really remember. I knew Mike stopped by one time to complain about Sandusky, but I don’t think he said that.
Investigator: C'mon Joe, we need your testimony to put this monster away. We already have a boy who tells us he was raped by Sandusky. He is certainly a pedophile, we just need the strongest case possible. Mike says he wasn’t that explicit when telling you, but do you remember him saying Sandusky was fondling him?
Joe: Hmm, that sounds more reasonable, maybe he did say something like that
Investigator: Joe, you are not in trouble. You did the right thing by notifying Curley and Schultz. What Mike saw had to be of a sexual nature, otherwise you would have not got those two involved. Also Mike has been such a good assistant coach for you. You could definitely trust him, wouldn't you agree?
Joe: Hmm, I guess so
Investigator: Awesome, you are going to be an excellent witness. You’ll really help us put that sicko away
I don’t really see arm twisting here either. Maybe some leading questions but not arm twisting.