I feel like this is kind of a cop out, and if it's how things work then it should be re-evaluated.
Otherwise if you had a Michael Jordan-esque mafia player you would by definition have to rate them the highest no matter how they performed. Because it is common knowledge that they are the best player.
Your follow up point about Gorf's "open book" playstyle is a more reasonably approach to have, and you could argue that this constituted "playing the best" within the game.
But the way you phrased it makes it sounds like your knowledge of who the best player is all that matters for the vote regardless of individual performance. idk
It's about who showed that they are the best player in the game. Not based on outside knowledge.