You know what's really funny is that regular Mawile has LO Sheer Force Iron Heads with no drawbacks that are on par with Hammer.
252 Atk Tinkaton Gigaton Hammer vs. 0 HP / 0 Def Mew: 181-214 (53 - 62.7%)
252+ Atk Life Orb Sheer Force Mawile Iron Head vs. 248 HP / 0 Def Mew: 183-216 (45.4 - 53.5%)
252+ Atk Huge Power Mawile-Mega Iron Head vs. 248 HP / 0 Def Mew: 247-292 (61.2 - 72.4%)
Of course LO or Band Hammer will do more damage but come with substantial downsides. Mawile can just click whatever and that isn't getting into the rest of its movepool. Tinkaton has to use sort-of Banded Hyper Beam to out-damage Mawile.
Yeah, Sheer Force also has the added benefit of boosting Mawile's STAB Play Rough and Crunch + no LO recoil, while Tinkaton's Play Rough is gonna be hitting like a wet noodle. Mawile's main issue is that all its stats are unbelievably bad outside of attack and defense, so Tinkaton will still probably be better Pokemon, but Mawile is arguably more interesting due to having better abilities.
Its a shame really. I wanted Tinkaton to be a strong OU Pokemon with good stats. I though that it'd at least have better stats than Mawile, and while that is largely the case, its lower in the two most important areas of Attack and Defense. Instead, they gave it a very weird stat distribution and made it another one button Pokemon largely carried by its signature move. I think its a bit boring frankly. Still, I may be a bit too harsh on it since it still has a solid movepool with options like Stealth Rock + U-Turn and one of the best typings in the game. Lanturn is similar Pokemon with rather underwhelming stats, but it gets by as a pivot just fine due to its unique combination of traits. I think Tinkaton could wind up being similar, with its typing and movepool giving it good utility on top of having a big Hammer to smack around most threats with.