There is no good answer to why, except to improve fingerprinting. Which is most of what this site shows, the amount of data a site, even open in the background, can use to continuously fingerprint you. Or maybe I misjudge what this is supposed to do.
I believe that you think that your answers are true but my desktop will report 12, my work laptop will report 16, my macbook will report 16 as well, my work desktop will report 64 (my surface laptop will report 12 as well, my ipad pro will report 6... I can continue this for some time).
Which machine do you think has the best performance for your app?
Those numbers actually mean something. That’s approximately how many concurrent threads I would want to use. I’m not sure I follow the point you’re making