Those words were about the JPEG recompressor (Brunsli) specifically, which saves about 22% but has a smoother transition from today's .jpg world than any of the new lossy formats; you can bit-for-bit reconstruct the original JPEG from the Brunsli-compressed one, and it's certainly much faster than AVIF to encode with CPUs. You can even insert Brunsli as a Content-Encoding that's transparent to the user (so right click still saves .jpg), and Chrome had an issue open to consider doing that before they backed out JXL support.