Sacrosanct
Legend
Except that's not part of the Attack action. Flurry of Blows states that your extra unarmed strikes happen "Immediately after you take the Attack action". Still, you probably only losing a couple points of damage anyway.
Flurry is a different monk ability than the unarmed strike monks get when declaring an attack action. Let me ask you this. If the unarmed strike a monk gets after declaring their attack action is just a bonus unarmed strike, then why call it out? Every PC can use a bonus action to make an additional unarmed strike if they want. It's treated the same as duel wielding, only instead of a dagger or sword, it's your fist you're using.