those numbers are nonexistent for most distribution, since forcing telemetry isn’t really a cool move in the free software world
The number of IPs hitting their software repos can be a decent way of estimating active users. Also, ISO downloads and so on.
Local repo mirrors are pretty standard in the enterprise world are they not?
Any company invested enough to host a local mirror will not give a blank install of Ubuntu to their employees though.
You can argue that other distros are popular as well, but when it comes to the “I’ve heard of this Linux thing, let’s try it out” crowd Ubuntu is the goto option, no doubt about it. And the impact on this crowd is exactly what is discussed in the article.