Note that the 84% number is for a prototype model... 77% is for an on-the-market model, and it is beaten in efficiency by conventional electric for cookware matched in size to the heating ring.
Also, while gas is 'just a flame', the heat mostly rises, and right above it is the pan. Noticing that the pan, the hob, and the room feel warm/hot afterwards can be deceptive because the specific heat capacity of metal is 8x lower than that of the water in the food you're cooking, so you'd likely underestimate the efficiency.
Note that the 84% number is for a prototype model... 77% is for an on-the-market model, and it is beaten in efficiency by conventional electric for cookware matched in size to the heating ring.
Also, while gas is 'just a flame', the heat mostly rises, and right above it is the pan. Noticing that the pan, the hob, and the room feel warm/hot afterwards can be deceptive because the specific heat capacity of metal is 8x lower than that of the water in the food you're cooking, so you'd likely underestimate the efficiency.