Based on Soros' past, it's probably a combination of both. For example: https://en.wikipedia.org/wiki/Black_Wednesday . In the 90s he saw that the UK's commitment to prop up the Pound Sterling was ill advised, but he made sure that his short position paid off by systematically selling Pounds until the government had to renege on the exchange rate mechanism.

What's the difference? If somebody bets money on X, you can suspect he's more likely to work for X than against X.

If he didn't really believe what he was saying, he wouldn't have bet such a large amount of money on it. There is no reason to believe he is lying. Whether he is correct is another matter, but he's not "working for/against" anything, he's just stating his actual opinion.