it seems like it's a little bit more than April? Doesn't mean it isn't the biggest in a few years, but it's not like it's head and shoulders above. August and July look like they were fairly slow months so the gain in the 30 day average is kind of a skewed stat when the article's talking about it being special int he span of years.
Since they linked to the steam charts themselves I assumed they were talking about concurrent players. But maybe they were, I just thought it wasn't significant