IOW, if you're "modest", and you can handle basic logic
Presumably, if we have more than one person in view (say, X and Y), we could mark the belief operator to say which believer we're talking about. So BXp would mean "X believes that p".
The wiki links to https://en.m.wikipedia.org/wiki/L%C3%B6b%27s_theorem to explain why it should be true, and the theorem seems to fall into the same problem.
Also, it says that type 4 reasoners are modest, and implies that type 4 is pretty good ("increasing levels of rationality"), so"modest" seems like a "good" descriptor.
This is why you dont get work done.