Counterwatch does not count as a special ability

Counterwatch - Gain a heal over time effect (15%), Retribution, and +50% Offense for 1 turn. These Buffs cannot be dispelled. In addition, gain a 50% chance to call an assist until the end of battle when attacking out of turn.

Captain Rex unique says : Whenever any other Phoenix ally uses a Special ability, Rex assists dealing 40% less damage. 

Hera Lead says : Each active Phoenix ally grants their Unique ability to other Phoenix allies. In addition, whenever a Phoenix ally uses a Special ability, they gain 20% Turn Meter if Hera is active. This effect is doubled for Phoenix allies with less than full Health.

X1.png you can see hera about to use the counterwatch special ability 
X2.png you can see the targeted stormtrooper was not damaged at all, and Hera gained 20% TM. 

Counterwatch should have triggered captain rex unique calling all phoenix to assist on the stormtrooper.

If you compare X1 and X2 you can see Hera gained 20% TM from her lead, so the counterwatch did count as a special ability for her lead but not for Captain Rex unique.

BUG

Military Might Assault battle grants allies a special ability called Counterwatch.
Counterwatch triggers TM gains but not the assists when used with the phoenix team.

BUG Reproduction

Military Might Assault Battle use phoenix with captain rex + hera as their lead.
Use the counterwatch ability.
Observe as they gain TM from Hera Lead but No assists from Captain Rex unique.