I just had to beat the single headed panzer 11 times for the achievement to pop up and to get the medal.

Did you get the first win right after they were released? There was a little glitch where the achievement wasn't counting wins, but that was fixed around 1 o'clock this morning.

No, I saw the news post like 10 mins before I posted here, beat the challenger 11 times, and came here to post about the bug

It worked fine for me just now.