Surely nobody could interpret this as beating an arbitrarily lossy format. I could just erase the entire input, after all. One would have to incorporate quality into the metric. Because of that, it seems natural to assume they mean lossless.
If a given lossy format is inefficient enough, then it’s possible for a lossless format to beat it at compression. I initially interpreted the website as making the surprising claim that FLIF beats several popular lossy formats while itself being lossless. Most people understand “JPEG” to mean the popular lossy format, JPEG. The site could be a lot clearer that that they are actually comparing it to lossless JPEG, lossless WEBP, etc.
