This is a bit misleading. All of genkernel/, gentoo-kernel/, gentoo-kernel-bin/, gentoo-sources/, git-sources/, vanilla-kernel/ and vanilla-sources/ are all different packages for the same Linux Kernel. There are multiple slots per package for the various supported LTS versions of said kernel but they will all get +/- the same set of patches for these issues. There is some support for other kernels like Darwin, BSD and HURD but your millage will vary.
https://wiki.gentoo.org/wiki/Kernel/Packages/en