I agree with mkoeppelmann. Talking about "correct with reality" is nonsense, because it isn't measurable.
Instead we should discuss the average belief of distributions of users.
It seems to me that the distribution of users who's opinion most matters is the distribution of coin holders.
If we use the distribution of betters, then whichever side is selling shares cheaper will win. It would be bad.
If we use a subset of the coin holders, then it will be possible to bribe the oracle to cheat.
The distribution of coin holders is the only distribution of users who's opinion we can use as an oracle.