They remembered to cover Google.com (it gets perfect scores), but forgot the testing site itself.
And it pretends to have a better score than a static html page without any ressources.
The screenshot shows some text among the lines of "We're sorry... ...but your computer or network may be sending automated queries. [...]". It looks like some kind of abuse/DoS protection was triggered.
It's not quite that simple, but that's the basic idea.
Put it <style> tags in the <head>. No reason to use an external file for so little. It's not worth the overhead.
* - I don't know if that's a real expression. It doesn't even seem to fit, but I like it so I'mma keep it.
https://www.smashingmagazine.com/2015/08/understanding-criti...
There's no point making all visitors cache a CSS file when only a tiny minority will need it.
Note that I live in the middle of the Pacific Ocean, so HTTP round-trip times are terrible for most users. If you're on a first-world connection, it shouldn't matter as much.
I could kind of get it if webp was an apple or ms solution but it isn't??
It's always going to be arbitrary to have an absolute measure given the diversity of sites. Large/slow images are going to be normal for photography sites for example but worth knocking points off for coding sites. You're better off using it as a relative measure to see if the same site is improving when you make changes.