Yes, that explains their methodology but not the location of the hardware. If I go and run a Lighthouse audit on localhost vs. a server in Philadelphia there's going to be an inherent difference.
Anyway, it suffice to use gitlab, github, bitbucket and sourcehub for a few seconds to notice the slowness of the three first sites compared to the last one.
We didn't really need the numbers to be convinced but I hope they will produce some pressure to be faster.