If I accept the premise that it is programmed in such a way that it reports its internal processes completely and honestly, then I agree it can't "hide" its thoughts.

That said, if we're talking about a superhuman intelligence -- or even a human-level intelligence, come to that -- I'm not confident that we can reliably predict the consequences of its thoughts being implemented, even if we have detailed printouts of all of its thoughts and were willing to scan all of those thoughts looking for undesirable consequences of implementation before implementing them.