For example:
A Gyarados with Bite?! A Nidoking with Double Kick! A Mamoswine with Peck?! A Dugtrio with Astonish?!
I really don't know why this is, so is there even a reason?
In the early stages of any Battle Factory, the Pokemon they give you have horrible Movesets to make the earlier stages more challenging for you(As the AI are weak). As you get to the 2nd and 3rd Runthrough, the Movesets get better.