It's been standard for longer than I've been alive to overload $OS_NAME to mean all of the following:

kernel

kernel + default userland

Kernel + default userland + kernel vendor add-ons

kernel + default userland + kernel vendor add-ons + ecosystem software

Also, since linux gained traction OS can frequently be interchanged with distribution of a kernel + userland + packaging tools + software repository + ecosystem, in various ways, and as above.

Not sure why you decided that OSX means strictly:

kernel + default userland