For Using Spheres of Might, gaining talents in Boxing, Brute, Open Hand, and Wrestling spheres gain increased unarmed damage. If you already have unarmed damage, 3 talents just increase your size category for unarmed damage.
Under Equipment Sphere, Monk Weapon Training (discipline), if you have this talent, Flurry of Blows, or Brawler's Flurry, any time you take an attack action, you can take a -2 to all attacks and make another attack with any weapon this talent would grant proficiency in.
When do these rules ever come into play?
-Brutal Pummeler for the Brawler loses his Unarmed Damage and Brawler's Flurry.
-Sundering Hand and Drifting Lotus for the Monk lose Unarmed Damage and Flurry of Blows.
-Street Fighter loses both but gains a worse version of the Equipment talent, being locked out from using Flurry with the Dual Wielding Sphere.
-Beastsoul, Shadow Boxer, and Yamabushi don't grant Sphere of Might talents or progression.
These rules don't seem to ever come into play unless another class randomly gets Flurry of Blows/Brawlers Flurry. I know some archetypes can give unarmed damage, but it seems weird that random archetypes can gain the increased damage but the star unarmed Monk and Brawler can't.