The attack bonus listed for the monk's Flurry of Blows (FOB) is not a Base Attack Bonus. It is the monk's BAB adjusted for the penalty he takes when he uses FOB, and including his extra attacks from that. They actually spelled this out in the text fairly well.
When unarmored, a monk may strike with a flurry of blows at the expense of accuracy. When doing so, she may make one extra attack in a round at her highest base attack bonus, but this attack takes a -2 penalty, as does each other attack made that round. The resulting modified base attack bonuses are shown in the Flurry of Blows Attack Bonus column on Table: The Monk. This penalty applies for 1 round, so it also affects attacks of opportunity the monk might make before her next action. When a monk reaches 5th level, the penalty lessens to -1, and at 9th level it disappears. A monk must use a full attack action to strike with a flurry of blows.
If he progresses to the 11th level of monk, he gets Greater Flurry, which seems to be a separate ability (which grants
another attack at full BAB, with no penalty by this point, when he uses FOB). So even with something that let you stack monk with something else to progress FOB, you still wouldn't get Greater Flurry unless the text specifically said so.
So Flurry works kind of like TWF, but the penalty gradually goes away entirely, and if you go to monk 11 you get Greater Flurry, which gives you another attack. You also add 1xStr to all of your attacks made during a flurry, unlike TWF with that 0.5x off-hand business.
