Yeah, even on that fair; jpg-unfriendly example jpeg still clearly beats flif above 22kb. And below 22kb - sure, FLIF is less bad, but it's still unusable. Also, the examples below 22kb are a little unfair to most codecs in practice, since you'd get far better results by downscaling first.
Here is the correct link: http://flif.info/example.html
And yes "well" is relative and what I meant by that is that its not readily easy for a normal user to do it.
BTW I think Flif is damn good particularly progressive decoding. Its unclear how good HEIF progressive decoding is.