"A recent audit revealed that traces of milk residues can still be found on manufacturing equipment despite intensive cleaning."
I guess because they now know for definite that the products definitely do contain milk, they can't get away with the 'may contain traces' any more. They're probably more concerned about getting sued by people with serious milk allergies, but if they're admitting there's definitely milk in the chocolate then they can't say it's vegan any more.
But yeah, I'll be sticking to other brands - my recent discovery is Organica chocolate, and the vegan 'milk' chocolate buttons they sell in Holland and Barrett. Makes a change from 70% stuff all the time!