That’s mostly reflect the split of kwin-x11 out of main kwin repository.
The link should be to:
Many distro will do the same with Plasma 6.4, but that will depend on their policies still.
So Arch gets rid of x11 before “Plasma 7” even exists hahahahah.
Plasma 7 may remove the kwin-x11 package later. That’s way different to making it opt-in.