It's not really a contradiction. Increasing the chance from .0000001% to .000002% is not just increasing, but DOUBLING the chance of something, but still means that there is very little chance of it occurring. (Numbers not related & for illustrative purposes only)
They don't go into numbers, but it's basically along those lines. TLDR from the article: Quake swarms *can* mean that a larger quake is coming, but they do not believe that it is the case based that they have had several swarms in the area recently.