To me, it doesn't matter what they're defining it. Resolution and progressive are matters.
It just HD uses advertisement or marketing for higher(beyond&beyond++) resolution every time they make brand new ANY devices in the future overtime just blowing your mind while "SD" this defines a legacy resolution for old devices.
I heard they're slowly dropping "HD, QHD, UHD", instead they use errr #K referring resolution in short as an advertisement. Yeah, it's quite annoying, but whatever carry on lol