So while I was running through some grass I decided I wanted to put a different pokemon first, and right when I did that I got into a battle and well... this is what happened
Now when you actually use a move it will be a move of the pokemon that is out on the field. So for example if I were to use surf I would use thundershock because that is where it is at on my mareep.
In order for this bug to take affect you have to switch pokemon a split second before battle, so basically you'd have to guess when you would enter battle.
I don't think the bug is that big of a deal just thought I'd report it in.
Also if this has already been reported and addressed I'm sorry for reposting the same bug