They can probably reach the same conclusions about why there might be more installs than downloads by thinking about it for maybe 5 seconds instead of tracking people.

Easiest explanation off the top of my head, without reading the article, would be IT departments including Firefox in their base image they use on all their standard issue computers, resulting in hundreds and possibly thousands of different installs having the same download ID. That alone by itself would cause an absolutely massive discrepancy between download and install numbers. My company includes Firefox in our base image and it's on at least 200,000 different laptops and desktops, with a handful of different download IDs between them depending on when they got issued the computer.

Not just companies. I somtimes do this at home to save bandwidth / download time and then install software from usb stick.

The reasons are easily seen though. Corporate IT departments autodeploying, Linux packaging repos, people compiling from source.

Also, they could just ask, instead of adding more spyware. Like a survey.

Playing your game, why would Mozilla need to know this?

I wonder of they are confused by apt-get install firefox.

(Joking, but only a little.)