BUG Focused Thrust not effective with Prime Strike

I ve bought a Constricting Command Viper Cap with Require 5 fewer enemies to be Surrounded.

All other melee skill with spear like Rapid Assault will get more damage by allocating Focused Thrust 75% increased Melee Damage with Spears while Surrounded

But Prime Strike, a melee skill with spear, get no more damage then.

A big Bug, please fix it. thx a lot

any help？
have u noticed that？thx

any reply?