I love aviation vaporware. All sorts of crazy claims, with not one shred of actual aerodynamic reality.
The Honda jet is a prime example. Crazy claims, sub-par real world speed, payload and range. Today's passenger aircraft are very well refined, highly aerodynamic, and today's engines maximize the ability to convert jet fuel into high speed thrust.
One more interesting example. GE's Passport engine initially claimed 25% improvement in fuel specifics, due to the use of ceramics and other technologies such as bladed discs (one piece rotors and blades) . The claim was then reduced to 8% improvement in TSFC (take off thrust fuel specifics) Reality is another story altogether, it seems we are looking at a 2-4% improvement over older designs, and possibly a difficult to discern improvement over the BR725 in real world use. GE and Bombardier made claims of incredible range and speeds. The reality is that their newest aircraft falls short of the speed, range and fuel consumption of the BR725 powered G650ER Gulfstream has been selling for years.
My point is that we've spent a lot of effort getting it right over the last 70 years. I'll be surprised if we see any substantial gains in passenger MPG, which hovers around 100 passenger MPG on our best aircraft and routes today.