Nah, your view is far too one-sided. Orehi himself readily rejected all the theories by the filming crew. Then he went forward, without consulting the other Classics club members overly much (especially afterwards, before presenting it to the filming crew), with finishing the script. It got made into the film before the others had a chance to say anything about it. I think they were indeed justified in being disappointed with it; they had been under the impression Oreki tried to complete Hongou's text, but it was immediately clear to them he didn't but wrote his own. It's true they had unreasonably high expectations, but Oreki equally got unreasonably far ahead of himself after the praise by Irisu.