Where did you get the information that Apple will never support JPEG XL?
I haven't heard or seen anything from Apple, neither in favor nor against JPEG XL.
I would assume though that when Adobe and Serif (and their open source alternatives like Gimp, Krita, and darktable) are adding JPEG XL support in their products, there will be some incentive for Apple to add it in their products as well. After all, they do have nice HDR-capable screens now, so it would not really make sense for them to not support the best codecs currently available for HDR, which are AV1 for video and JPEG XL for still images. Apple does have a long-standing reputation for being excellent in high-fidelity image workflows, and I don't see how they would be able to keep that reputation without adding support for JPEG XL.
So I don't see why Apple can't just support both AVIF and JPEG XL. AVIF is 2-3 years older so of course they'll land support for that one first, but I don't think that should be seen as an indication that they'll not support JPEG XL.
I believe Apple will be the second major OS to add JPEG XL after Linux distros. They understand user value in the creative space. Creative work occasionally needs more than 12 bits, no surprises approach to quality, and performant lossless coding.
I haven't heard or seen anything from Apple, neither in favor nor against JPEG XL.
I would assume though that when Adobe and Serif (and their open source alternatives like Gimp, Krita, and darktable) are adding JPEG XL support in their products, there will be some incentive for Apple to add it in their products as well. After all, they do have nice HDR-capable screens now, so it would not really make sense for them to not support the best codecs currently available for HDR, which are AV1 for video and JPEG XL for still images. Apple does have a long-standing reputation for being excellent in high-fidelity image workflows, and I don't see how they would be able to keep that reputation without adding support for JPEG XL.
So I don't see why Apple can't just support both AVIF and JPEG XL. AVIF is 2-3 years older so of course they'll land support for that one first, but I don't think that should be seen as an indication that they'll not support JPEG XL.