Its actually roughly the same, I think Eviolite influenced the calculations my dude. You also should calulate with EVs, because that mattersThats not correct. A mon with 50/100/100 is significantly bulkier.
0 Atk Landorus-Therian Earthquake vs. 0 HP / 0 Def Eviolite Chansey: 172-204 (50.4 - 59.8%) -- guaranteed 2HKO This chansey has 100 hp and 50 def.
0 Atk Landorus-Therian Earthquake vs. 0 HP / 0 Def Eviolite Chansey: 100-118 (41.4 - 48.9%) -- guaranteed 3HKO This chansey has 50 hp and 100 def.
0 SpA Mew Genesis Supernova vs. 252 HP / 252+ SpD Mew: 72-84 (23.6 - 27.6%) -- 81.2% chance to 4HKO (50 HP)
0 SpA Mew Genesis Supernova vs. 252 HP / 252+ SpD Mew: 108-127 (26.7 - 31.4%) -- guaranteed 4HKO (50 SpD)
0 SpA Mew Genesis Supernova vs. 252 HP / 0 SpD Mew: 99-117 (32.5 - 38.4%) -- 99.1% chance to 3HKO (50 HP)
0 SpA Mew Genesis Supernova vs. 252 HP / 0 SpD Mew: 172-203 (42.5 - 50.2%) -- 1.2% chance to 2HKO (50 SpD)