Harshly is two stages, right?
I’m playing SP and Chimchar used Leer, says it harshly fell. Isn’t that two or three stages when it’s supposed to be one?
Simple doubles the effectiveness of stat stages.
Source Like AlphaSapphire said, it's the reason most likely. One of Bidoof's Ability is Simple and it's common in the wild, which is why Defense harshly fell.