It is a valid question that is intriguing a lot of folks. How is so much wood packed into this a bat of such low dead weight? Maybe there can be a constructive debate on it?
Is it simply because the weight is taken from edges and the top? That alone cannot explain because based on that logic it should not dwarf the MMI.
Light willow? BlackCat said earlier that it was not over-dried. So do they have a disproportionate share of low density naturally dried timber? Something different they are doing in growing their willow? If that's the case it could be a huge advantage over competition who is relying on other suppliers for willow as well as bat making.
From the pictures, can't make out any other weight reducing tricks.
Either way, scientific or not, the design deserves a lot of praise for innovative thinking.
Rich - what's your take on this given your experience and the minor detail that you've actually had the bat in your hands