Notes: The function only returns true while the ped is:
A.) Swinging a random melee attack (including pistol-whipping)
B.) Reacting to being hit by a melee attack (including pistol-whipping)
C.) Is locked-on to an enemy (arms up, strafing/skipping in the default fighting-stance, ready to dodge+counter).
You don't have to be holding the melee-targetting button to be in this stance; you stay in it by default for a few seconds after swinging at someone. If you do a sprinting punch, it returns true for the duration of the punch animation and then returns false again, even if you've punched and made-angry many peds