How would building packages for SDK work without inheriting nativesdk?
All other packagegroups in this variable use $MACHINE to parametrize themselves, so they are not plain packagegroups either.
Furthermore, they inherit cross-canadian which sets PACKAGE_ARCH in the same way nativesdk.bbclass does.
I cannot know every single detail and history behind why oe-core works the way that it does.
What I do know is that I cannot add certain packages to SDK packagegroup because an unrelated error check is producing a false positive because the possibility of an allarch override is not being accounted for.