I believe you are mistaken. 'Each player calculates their victory points by adding together the figure cost of all their opponent’s destroyed figures' is very clear instruction to count VPs per figure, because 'figure cost' is an actual game mechanic term and 'all destroyed figures' clearly means, well, all of them, not just the ones that had their entire deployment group destroyed. The part after the dash is just a clarification specifically regarding scoring VPs for attachments. That's the only instance in which taking out full deployment groups matters for VP purposes and that's why it's separated from the first provision by a dash.