Aren’t these metrics fake anyway, Linux user dont usually want software to track them, who’s counting everyone and with what as a data source. There is no fair collection point, the best data collection point in my mind would be UA stings on ad networks, but then the metric is users who dont use an add blocker, or users who use facebook. These factors atleast, are certainly not independent of a users choice of operating system. I believe that gnu+linux users are likely to be very underrepresented.