I don't really know how accurate this is, but achieving such a high win rate is almost impossible in real life. Even if he consistently bets on low odds, there will still be times when losses are unavoidable. Eventually, his losses could outweigh the profits he makes from winning predictions. For some reason, I find it hard to believe that his win rate is genuine. As someone mentioned, it could simply be a promotion for the platform to attract more players. Whether it's gambling or predictions, the concept is still the same, and the chances of maintaining such a high win rate are extremely low.
For the prediction market I think this can still be done but it depends on the risk taking of The Gambler himself and if you look at what the OP conveys in the link it can be seen that the focus of this gambler is not to take a big profit in the bets he does but takes a little and is consistent.
This is what is sometimes difficult for most other gamblers to do because sometimes when it is profitable it is very rare that we immediately go out until the maximum profit is felt.
In contrast to the gambler when taking profits of only $1 in every bet he makes but consistent in all bets made then this is of course a gap for him to maintain his winrate.
Not all gamblers will be able to do that even I personally feel that I will be very difficult to follow in his footsteps because in this case keeping emotions and not being too greedy is a little difficult for me to do.