In the webdev community it's well known that good performance is very important for user satisfaction, and that's backed up by research. There are no ideal metrics, and unfortunately every single one of them has some dumb edge cases. You could endlessly bikeshed which metrics could be better, but this particular set is not unreasonable.
It makes sense for search engine to pick websites that not only have the relevant content, but also are able to actually get that content on screen without frustrating users with slow-loading crap that makes browser freeze and stutter.
Keep in mind that your high-end desktop web experience is in minority. The web is now mostly mobile, and mobile is mostly low-end Android. That's a shit sandwitch, and it desperately needs an intervention.