Isn't this thing like the ultimate Stallbreaker?

Mold Breaker bypasses Unaware, at +1 it 2HKOs most Stall Pokemon with dual STAB alone and can set up a Substitute very easily versus Stall, like against a Quagsire.

Was thinking of using one paired with a Healing Wish user. This thing is an underrated threat.

>+1 252 Atk Mold Breaker Mega Gyarados Crunch vs. 252 HP / 112 Def Mega Sableye: 169-199 (55.5 - 65.4%) -- guaranteed 2HKO
>+1 252 Atk Mold Breaker Mega Gyarados Waterfall vs. 248 HP / 252+ Def Clefable: 196-232 (49.8 - 59%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
I've seen a lot of SpDef Unaware Clef specifically for Manaphy, too.
>+1 252 Atk Mold Breaker Mega Gyarados Crunch vs. 252 HP / 136 Def Amoonguss: 252-297 (58.3 - 68.7%) -- guaranteed 2HKO after Stealth Rock and Black Sludge recovery
>+1 252 Atk Mold Breaker Mega Gyarados Crunch vs. 252 HP / 252+ Def Quagsire: 178-211 (45.1 - 53.5%) -- 39.5% chance to 2HKO after Stealth Rock and Leftovers recovery
Not like Quagsire is doing anything back. Can't even break Gyarados' sub at -1.
>+1 252 Atk Mold Breaker Mega Gyarados Crunch vs. 4 HP / 252+ Def Eviolite Chansey: 297-349 (46.2 - 54.3%) -- guaranteed 2HKO after Stealth Rock
>+1 252 Atk Mold Breaker Mega Gyarados Waterfall vs. 252 HP / 252+ Def Togekiss: 166-196 (44.3 - 52.4%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
>+1 252 Atk Mold Breaker Mega Gyarados Waterfall vs. 252 HP / 244+ Def Seismitoad: 195-231 (47.1 - 55.7%) -- 77% chance to 2HKO after Stealth Rock and Leftovers recovery

Whats up? You'd think with how much Stall is "dominating the meta", Mega Gyarados would see more use, yet he's chilling at 2% usage.