They're talking about daily P/L. They realize profit and loss every day. You can't simply ignore all the days when you had (unrealized) losses and still compare with situation described in the article.
Yeah, it's the same thing at very different time scales.
In other words, the standard deviation for 3-year returns is much lower than the daily standard deviation.
You can get a positive return in 3 years without being especially good or lucky. But getting a positive return every single day for 3 months is extremely unlikely.
They're talking about daily P/L. They realize profit and loss every day. You can't simply ignore all the days when you had (unrealized) losses and still compare with situation described in the article.