HBD had some beginner's luck there - had the 20% Savings campaign managed to print more, there would have been a serious HBD de-peg already. Barring a miracle, HBD is still going to lose the peg later this week and people are going to learn a few lessons for discounted price.
I am not a fan of the BTC vault concept but if we want to be result oriented, it is fair to admit HIVEBTC fell down considerably so the partial BTC-backing of HBD would have been helpful in this particular scenario. It would hurt in others, so the anecdotal evidence does not prove anything.