Am I missing something? Between mixers and single-use addresses - not to mention every mundane transaction that hasn't opted into into this tracking scheme - the odds of them being able to say much about a typical address seem practically nonexistent.

I can see some strong similarities to DRM. There are large organizations that would very much like for a technical impossibility to exist, leading some to step forward to sell a fundamentally flawed patchwork to them whose primary impact is inconvenience for end users.