Half-truth. By default AVIF is optimized for low file sizes. When you change a few settings Jpeg XL isn't that much better than AVIF for visually lossless images. It WOULD be nice if these settings eventually got enabled be default in a "photo" preset option.
avifenc -d 8 -y 444 -s 6 -q 84 -j 1 \
--cicp 1/13/1 \ # sRGB mainly used by PNG/GIMP
-a qm-min=0 \ # Forces max quality ceiling in super blocks.
-a deltaq-mode=3 \ # Psychovisual augmentation + speed boost.
-a aq-mode=1 \ # Enables variance boost.
-a sharpness=2 \ # Sacrifices some efficiency for image clarity.
Encoding with codec 'aom' speed [6], color quality [89 (High)]
Encode time: 2.5 seconds
ssimulacra2: 88.41067333
585 KB
https://files.catbox.moe/f8dwbx.avif
Encoding [VarDCT, d0.790, effort: 7]
Encode time: 2.2 seconds
ssimulacra2: 88.45996710
514 KB
https://files.catbox.moe/ab80vn.jxl