Even that will fail if the price moves quickly before the hourly feed updates. Moving more than 5% within an hour is hardly unprecedented or even unusual. It's also simply not desired to create more HBD just because the price of HIVE happened to be different over a backward looking period, say from 1-2 days ago. If we had a feed of HBD, then indeed looking at an average price might be helpful, since this would indicate whether the peg had been held and if not, in which direction, but if basing it on the HIVE price, this sort of backward averaging makes no sense.

3.5 days in the future is just a more economically sound method, and the code to implement it already exists. The justification for it is the same in either direction.