Both repositories are following now the 4.9.x LTS branch, but :

• kernel generic is built from vanilla/upstream kernel from kernel.org ,

so works on all boards supported "upstream"

• rpi2 kernel is the one built from https://github.com/raspberrypi/linux

(that also rebase from upstream LTS but with their patches added in for the rpi2/rpi3)

Lucky that the RPi seems to run, without the specific patches from the foundation.

BTW, we never had any image for rpi2/rpi3 that was using the kernel-generic repo

Weird. I installed in in mid july when I saw it, and downloaded from here http://mirror.centos.org/altarch/7/isos/armhfp/. Something must have gotten screwed up, the CentOS-armhpf-kernel.repo is dated from sept 1st.

I'll just swap the baseurl around, update and hope for the best :)