Ability Slot Changes between Gen III and IV?

[english09]

I'm currently trying to change an Aron's PID to match the new IV's I gave it and I'm getting inconsistent information from across serebii, PKHeX, and Pokegen regarding whether Ability Slot 1 is Sturdy or Rockhead. When I use PKHeX to import my Aron from a Gen III file format to Gen IV+, it says it had Sturdy (as it does in-game), and says that Sturdy is Ability Slot 1.

BUT, when I search my Aron's PID with PID-IV.exe, it says that this PID could only have Ability Slot 2.

Am I missing something here? Did they switch from Gen III to IV? 

[theSLAYER]

If I'm not mistaken, odd PID is ability 1, even PID is ability 2.

However, if it is transferred from Gen III, it's ability doesn't change until it evolves, if I'm not mistaken.