Underneath the progression table there's a note that says:
Base Attack Bonus: Note that, like a monk, a drunken master makes unarmed iterative attacks at a -3 penalty, not the usual -5 penalty.
I for one find this to be rather intriguing. Especially because the Drunken Master has BAB progression as a fighter. I think that, theoretically, this means that someone could manage to get unarmed attacks at 20/17/14/11/8/5/2. More importantly, though, what happens if you only take one or two levels as a Drunken Master? Do you continue to get the better attacks, or do you only take them into consideration up the level that you took Drunken Master at, and take them under the same rules as multiclassing with a monk? I think that the latter seems rather odd, because it means that a person who takes one level of Drunken Master at level 20 gets a much better rate of attacks than someone who took one level at level 10.