Stat order weird in Calculators?

I think it's because in the game the order is HP/ATT/DEF when you use the appraisal

Because that's the right order. The game goes HP, ATK, DEF.
It's everyone else using a weird order because we rank ATK first.

When IVs were first discovered and subsequently data mined, the Atk/Def/Stm order quickly became a standard for various online calculators because that was the order they were listed in the data mining and attack is weighted more in the CP calculation.

Later when appraisal was added in game, some calculators decided to switch to the HP/Attack/Defense order because that is the order given in appraisal.