FWIW most people have called this a sticky footer since the dawn of Web 2.0. Go back ten years and you’ll find posts describing the sticky footer that should be at the end of the content (if the content goes below the fold) or the bottom of the browser window, if the content doesn’t push the footer there.
I understand the point you’re arguing but at some point the thing something is called becomes it’s name.
If you want a name for your concept I’d call this a fixed-positioned footer which is explicit that it’s position is permanently fixed and won’t change. It also correlates with position: fixed.
tl;dr You’re concept of a sticky footer is different than the rest of the web development community so it’s important to realize that and not correct someone for being correct.
The popular usage of "sticky headers" had the opposite meaning of "sticky" compared to "sticky footers." The usage of this word to refer to the header behavior won out and was formalized as position:sticky in CSS3 Layout.
The problem now is when people use "sticky footer" in the former sense, it's misinterpreted. Note the other comments on this story.
I understand the point you’re arguing but at some point the thing something is called becomes it’s name.
If you want a name for your concept I’d call this a fixed-positioned footer which is explicit that it’s position is permanently fixed and won’t change. It also correlates with position: fixed.
tl;dr You’re concept of a sticky footer is different than the rest of the web development community so it’s important to realize that and not correct someone for being correct.