Has Dave confirmed that US August Starter kits will get 2 H boards shipped per order like the equivalent EU model to meet the minimum advertised spec?
Yes, he did.
You are buying kits (unless you bought individual h-boards). Therefore, if you paid for a number of 25 Gh/s kits, you'll obviously get an extra h-board for each individual kit to meet the advertised kit specs you paid for.
Similarly, if you purchased a full 400 Gh/s kit, then whatever that whole kit is missing in hashing power would be added ( i.e. perhaps around 3 extra h-boards) to meet the advertised specs of that kit.
Hope that helps.