Why is the site loading speed on mobile via testmysite.withgoogle.com so weird?

Question

Google

Checking the loading speed of my site. Testmysite.withgoogle.com by Google shows speed on mobile over 3g and 4g.
And very strangely, it shows my website loading speed of 4.8. I compare with 10 competitors: they all load much faster (2-3 seconds).
At the same time, when checking through Google PageSpeed, on the desktop, the indicator of my site is 98, on mobile 64. This is better than almost all of the same competitors.
I check on webpagetest.org (speed on the desktop), according to it, the speed of a full load is generally 1.2 seconds. It's better than all competitors.
I also looked at the download speed in Yandex.Metrica, it is a little lower on mobile than on the desktop, but normal 2-something seconds on average.
Why then does Testmysite.withgoogle.com show such data?

Answer 1

Due to the fact that from different parts of the world the content loading time is different

Answer 2

Look better with more professional tools.
Take gtmetrix and see in it what exactly is loaded into the waterfall.
loading.express in it, see what parameters you need to work with.
Well, it’s right that they write here that Google pagespeed is for an understandable assessment.

Answer 3

Another important point for acceleration is the optimization and compression of images on the site. You can optimize each image manually (through Photoshop, for example), or automatically (through special services). Here is an interesting article on this topic: https://pr-cy.ru/news/p/6831-kak-i-zachem-optimizi...