Using SSIMULACRA2, I've compared Intel's QuickSync Video to Nvidia's NVENC encoder across Linux & Windows. They compete against other dedicated encoding hardware for different codecs across different GPUs, including an Intel iGPU.
Using an image format supported by exactly one browser - one that has less than 5% of the market share - without providing a fallback - is a pretty questionable choice.
I can't imagine that the bandwidth savings are even remotely significant to justify such a choice over an optimized PNG, JPEG, or the nearly-universally-supported webp.
From the article, minecraft.jxl is 545275 bytes.
Using imagemagick[1] to convert to various formats at 8bit depth:
191875 36.39% csgo.avif
288048 54.63% csgo.webp
349204 66.23% csgo.heic
507882 96.32% csgo-8bit.jxl
511727 97.05% csgo-85.jpg
527282 100.00% csgo.jxl
960946 182.25% csgo-95.jpg
3665475 695.16% csgo.png
183935 33.73% minecraft.avif
266890 48.95% minecraft.webp
358482 65.74% minecraft.heic
490623 89.98% minecraft-85.jpg
522250 95.78% minecraft-8bit.jxl
545275 100.00% minecraft.jxl
1047533 192.11% minecraft-95.jpg
3018052 553.49% minecraft.png
(No, I did not see those JPEG-XL images because Chromium laughs at it.[1])
[1]: https://news.slashdot.org/story/23/04/16/002204/fsf-says-goo...