The tomato test is disingenuous - no one slices a tomato by pressing the knife straight down - you slice it to break the thick skin and follow with a slicing motion. The rest of the graph basically shows no difference between the force used for ultrasonic one and standard knife used inefficiently?
And yet, when people like to show off how sharp their knife is, dropping a tomato on it (blade-up obviously) and watching the tomato split in two is one of the favorite tests.
Probably (and precisely) because you can only achieve this with a knife that cuts very well.
