I'm imagining something more like the way we treat movie directors. When I see Michael Bay vs. Quentin Tarantino, I don't think that those people wrote the film, or set up every camera shot in minute detail, or designed the costumes, etc. but I know that they had a hand in arranging for all of that and it will all ultimately come through with their unique stamp on it.
But regardless of whether you think your new system would be better, it's not the current system. Surely the question of whether someone is lying by putting their name on a book they didn't write can't depend on some hypothetical future change to the meaning of authorship that hasn't happened yet.
Not even an AI thing, we don't. Ghost writing has been going on for centuries.
I don't like that! I agree it's dishonest and I wish we lived in a world where having been exposed employing a ghostwriter is a disgrace no public figure can come back from. I don't like that AI has made it worse, either. At least with ghost writing there are some contexts (politicians, celebrity bios) where you might suspect it, but in most you won't.
But, we do live in that world right now.