Interesting that they use this strategy. Essentially, high variance is good when the expected value of the game is negative. It increases the chances of success in a bad situation.

The maths of this can be found in the article "A Rule of Thumb (not only) for Gamblers." Currently, this article is available free here: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.55.3...