The double hip is just loading your hip (ie. not just taking it from where it is). In other words, Consterdine is doing the same thing as in the sochin kata video. This is good power generation, but you won't get that opportunity to pre-load in every instance.
You should practise a good hip load for power striking bags, pads, shields (or telephone books). But in kata? In the context of blocks?
Consterdine does it quite fast - but the millisecond it takes to do might be a millisecond too fast in a flowing, dynamic environment. Preloading your hip with every strike in a kata is not necessary.
Most karateka should be able (or should practise) using their hips. Confusing the static, ideal, environment for combat is another thing. So while I like what Consterdine is doing (and he has excellent hip use/power transfer), I don't think this is a template for kata practice.