It's because of the Chinese user influx during their holiday season. Valve is not correcting anything they are just showing the data. As usual, Phoronix is misinterpreting what they're looking at.
It's about oversampling. Due how the survey is sent, a massive influx of machines coming online all at once will be more likely to trigger the survey. They know the general composition of their users, so they need the survey to be around the ballpark of that.