He said 'if they had played both' not 'if this was a normal contest setting and they could vote for games they hadn't played'.
It's an interesting question that's been posed before. Some games in this contest are going to have an advantage because only the people that already really like those sort of games will have sought them out. If everyone in that match had played both games, you can't say HoM&M3 wins with any degree of confidence.
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Black Turtle did a pretty good job.