1. Do not track was not the browser deciding what to do (that would be a similar shape as Firefox multi-account containers and incognito mode). It was a machine-readable way to tell the site what to do; ie the same incorrect model as the click-through banners we have now, just non-interactive.

2. It was intended to be a way to communicate an actual intent from the user. Once it was set by default, it ceased to be an indicator of user intent.