I don’t see what problem an explicit id is solving here. While I do agree it should be possible to have explicit ids, they will suffer from the exact same synchronicity problem as implicit id’s. The link referencing the anchor will have to reference something. That something can change, whether it is an explicit id or the text of a header.
It is solving the problem that the auto-generated ID will change if you change the heading text or the ordering of 2 identically-named headings. Your anchor ID will stay the same unless you explicitly change it, meaning that your links to it will not get broken.