I'm sure they had good reasons to make the switch, but I don't really understand the argument about kernel and ruby versions. An upgrade to the newest LTS release would have gotten them ruby 3.2 and probably a newer kernel as well.
To resolve these, OpenStreetMap needed to switch to newer mainline kernels, naturally leading them toward Debian.
Because Debian is known for its up to date software, right? Gave me a good chuckle.