Low Description
The BooleanType validator accepts any byte (it only checks it's one byte long) and the comparator actually uses the ByteBuffer.compareTo() method on it's input. So that BooleanType is really ByteType and accepts 256 values.
Note that in practice, it's likely no-one or almost no-one has ever used BooleanType as a comparator, and almost surely the handful that might have done it have stick to sending only 0 for false and 1 for true. Still, it's probably worth fixing before it actually hurt someone.