Not sure if this glitched in some sort of way, or not. But when I got this I was not the highest scoring player in the game, but I was the highest scoring player on my team. We had also won the match, which it doesn't say is a requirement to earn the achievement.
Update: after testing Grimace has confirmed what he and I both experienced. That is that you only have to be the highest scoring player on your team. Win, or lose, it doesn't matter. Not sure if this is intended, so it could be patched in the future. So grab a group and take turns being the highest scorer. Good luck!!