You're right. The server and the desktop are two different worlds. Linux won the server world long ago. Windows dominates the desktop since the beginning! There are many more worlds: the embedded devices, smartphone market, tablets, etc. Yeah, one has to look at them differently. I was reacting to the argument often brought in favour of Windows, that you can get more support for Windows since there are more Windows users. That applies to the desktop world. On moodle.org there are definitely more Linux users.
https://w3techs.com/technologies. Never seen that before. There are other interesting breakdowns.