while I was battling in the battle maison a hariyama used fake out on my azumarill but azumarill used play rough normally.
The only explaination I can think of is this: Hariyamas ability is Sheer Force Sheer Force makes moves with side affects do more damage, but they lose the additional affect. Meaning its Fake Out did more damage but lost its ability to flinch.
Source: http://bulbapedia.bulbagarden.net/wiki/Sheer_Force_(Ability)
Sheer Force negates all secondary effects of an attack excluding recoil damage, stat drops and increase critical hit ratio.
Sheer Force prevents the secondary effect of the moves that the Pokemon that HAS the ability uses, not what is used ON the Pokemon. Darmanitan has Sheer Force, therefore his Fire Punch would be 33% stronger, but will no longer have a chance of burning. Likewise a Pokemon that has Sheer Force cannot use Fake Out to flinch an opponent.
Sheer Force prevents the secondary effect of the moves that the Pokemon that HAS the ability uses, not what is used ON the Pokemon.
Darmanitan has Sheer Force, therefore his Fire Punch would be 33% stronger, but will no longer have a chance of burning.
Likewise a Pokemon that has Sheer Force cannot use Fake Out to flinch an opponent.
Source