Google was a big part of JPEG XL and is actively working on libjxl as well... and JPEG XL is also based on FLIF and google's pik: https://github.com/google/pik so pretty weird.

On the chromium project there are many things that get added and pushed back for years but the commit and notes are there. Even the support for JPEG XL flag on by default itself keeps getting pushed back in it's thread. You can go here https://bugs.chromium.org/p/chromium/issues/detail?id=1178058#c38 and ctrl+f for "expiry_milestone" to see that it has been pushed back many times. Might be the case with the depreciation or something.

edit: they are seemingly finished and abandoning webp2 as well. All image formats seem out the window.