I think it is not BTC but it is mBTC. Afaik the denomination used at Fortunejack is mBTC when players are playing on the sportsbook. No matter what coins you use/deposit then your balance will be shown in mBTC when you access the sportsbook. I'm not using sportsbook at Fortunejack though, just saying it based on what I know when I visited it some time ago. If I'm correct, it means that his bet was 0.1mBTC and he won 50mBTC or 0.05BTC.
I have seen bigger wins anyway, I have seen as wins at thousands because I have been here for way too many years, and I have seen thousands of bitcoins won as well. This is why I think there is no bet that would beat those days in today's day unless some person decides to wager in hundreds of millions of dollars. Sure someone could beat the biggest bet in the dollar term but that would be tough challenge as well since I have seen as much as 9 million dollars won.
In light of all these, I still think this could be the bet with the most things in it, I have never seen 17 different games all come to a win all together, even one game with worse odds could happen but 17 different games even if all had 1.10 odds and seen guaranteed is a big challenge, you could have Real Madrid playing against 3rd division team 17 times in a row and there is a chance they may lose or have a tie at least once. That's why this is marvelous to me.