How do you think they got these metrics? People aren't going down there to do science or tourism without being able to communicate back home. It is almost always just statistics from the identifying header information of web traffic. It's not at all uncommon for web traffic from Linux programs to not identify the operating system. I know in my experience identifying as Linux in a browser would be more likely to cause problems than offer any benefit.
Yeah I feel like especially for like data analysis equipment which you would think there would be a lot of there. Stuff like that probably just has no way to get counted