Professional web developers want to create a great experience for their users, so they go beyond simply serving whatever comes off a digital camera.

As the article identifies, JPEG XL is kinda bad at certain types of images, whereas AVIF does well across the board, so if you feel compelled to pick a single format to use, AVIF would be a better choice, but it's definitely worth optimising your web images for the web.

Also, JPEG XL is two codecs bundled into one, VarDCT and Modular. So, even if you're picking JPEG XL as "the one codec", you're actually picking two, and you need to choose between them at encode time.