Do you mean the diagram following the sentence "Suppose we have calculated the expected information gained by potential truth booths like below:"?

Yes, that looks like a mistake -- a truth booth only has 2 outcomes, so it can produce at most 1 bit of information.

Regarding the other mentions on the page of information levels exceeding 1 bit: Those are OK, since they allow match-ups, which for 6 people have 7 possible outcomes, thus can yield up to log2(7) ≈ 2.81 bits.