“This is a simple yes and no question.”
Yes because this person has given interviews and created an autobiography, but little to none of the names were listed. Most people assume it was the actor Tim Robbins or Stephen King. In reality it could have been either as they both had read of Greene in newspapers at around the time Shawshank Redemption was set. No because there’s no solid evidence for one guess being more likely than another, so each individual would probably act on their own personal understandings or opinions when deciding which answer to go with.