You ask someone not to do a thing, and they promise not to do it. Then they do it. That's bad. End of Story.
Whether or not the result was a boon or a hindrance is besides the point. It is not the approach the developers wanted, and it was their decision to make.
If you don't trust OOP to the point where you disbelieve their official statements, what was OOP supposed to do to change your mind? You've already decided that they were lying to you. Were you a backer? If so, why'd you back a company who's word you don't trust? Weren't you? In that case, what the company says shouldn't have mattered until the book was out for sale, at which point: there is the product.
If you're a backer, yes. OOP, in my opinion, should have done more to keep you assured the project was moving (as backers are closer to investors than customers), but otherwise, OOP didn't owe you any proof or explanation. But even then, it was OOP's choice on how to placate impatient backers, and the leak was not in any way a favour to them.