These aren't all versions per se but mostly variants, versions and versions of variants. For example, we have packaged the xanmod kernel which is a modified kernel optimised for desktop use but it has two variants: Main and LTS. We have packaged both.

Here are the names of all of our kernels currently to give you an idea (as a JSON list):

[
  "linuxPackages",
  "linuxPackages-libre",
  "linuxPackages-rt",
  "linuxPackages-rt_latest",
  "linuxPackages_4_14",
  "linuxPackages_4_19",
  "linuxPackages_4_19_hardened",
  "linuxPackages_4_9",
  "linuxPackages_5_10",
  "linuxPackages_5_10_hardened",
  "linuxPackages_5_15",
  "linuxPackages_5_15_hardened",
  "linuxPackages_5_18",
  "linuxPackages_5_19",
  "linuxPackages_5_4",
  "linuxPackages_5_4_hardened",
  "linuxPackages_6_0",
  "linuxPackages_6_1",
  "linuxPackages_6_1_hardened",
  "linuxPackages_6_2",
  "linuxPackages_6_3",
  "linuxPackages_6_4",
  "linuxPackages_6_5",
  "linuxPackages_6_5_hardened",
  "linuxPackages_6_6",
  "linuxPackages_custom",
  "linuxPackages_custom_tinyconfig_kernel",
  "linuxPackages_hardened",
  "linuxPackages_latest",
  "linuxPackages_latest-libre",
  "linuxPackages_latest_hardened",
  "linuxPackages_latest_xen_dom0",
  "linuxPackages_latest_xen_dom0_hardened",
  "linuxPackages_lqx",
  "linuxPackages_rpi0",
  "linuxPackages_rpi02w",
  "linuxPackages_rpi1",
  "linuxPackages_rpi2",
  "linuxPackages_rpi3",
  "linuxPackages_rpi4",
  "linuxPackages_rt_5_10",
  "linuxPackages_rt_5_15",
  "linuxPackages_rt_5_4",
  "linuxPackages_rt_6_1",
  "linuxPackages_testing",
  "linuxPackages_testing_bcachefs",
  "linuxPackages_xanmod",
  "linuxPackages_xanmod_latest",
  "linuxPackages_xanmod_stable",
  "linuxPackages_xen_dom0",
  "linuxPackages_xen_dom0_hardened",
  "linuxPackages_zen"
]

(Note that some of these are aliases; linuxPackages_latest is currently linuxPackages_6_6 for example.)

Each of these has the following nvidiaPackages (modulo incompatibilities):

[
  "beta",
  "dc",
  "dc_520",
  "latest",
  "legacy_340",
  "legacy_390",
  "legacy_470",
  "production",
  "stable",
  "vulkan_beta"
]

(Again, some of these are aliases.)

This is useful to have because users might have hardware constraints. It's not hard to imagine a scenario where a user might have a WiFi chip that only works with kernel ABIs < 5.4 and require the 470 nvidia driver for their old GPU. Packaging just the latest kernel and just the latest Nvidia driver would make this user unable to use their system.