These are single measurements taken on one day, from one city, on one connection. Run the same test tomorrow and the numbers will move a little; run it from Europe and they will move more. That is why the date and conditions sit at the top of this page rather than in a footnote.
A fast score is also not the same as a good website. It says the page is built carefully and loads without waste. It says nothing about whether the writing earns attention or the thing sells. We’d rather be judged on both, but this is the half that can be measured.
Where a number is less flattering, it stays on the page. Busier sites carry more third-party code, and a storefront running payments, reviews and email tools will always block the main thread longer than a brochure site. We’d rather show that than quietly leave it out.