Interesting, although most cars now have an indicator on the dash wanting you to change up earlier.
Cars ? What are dey ?
In truth my car has such trickery too, and that's partly what gave me the idea. Petrol engines are most efficient at 100% load, and then at the rpms when when the engine is producing the most torque it is at it's most practical efficiency (at about 5000rpm for the 9er). But at lower loads, 30% for example, the most efficient rpm isn't necessarily still at 5000. The higher the rpm the more intake cycles there are, which means more fuel injection cycles, and those injection cycles will meter less fuel than if you choose a gear which requires 3500, which needs a little more throttle opening, but has 30% fewer intake cycles.
(Diesel peak efficiency is at about 65% load, which explains why my dashboard indications have me changing up gear even when my foot is flat to the floor !)
Although the manufacturers select gear ratios to give the best riding experience based on the engine's torque curve, a small nod is given to efficiency, but I think generally speaking 'riding efficiently' is a situation left for the rider to manage.
I'm curious enough about it to make something to check it out with anyway in the good old days you fitted a vacuum gauge to the inlet manifold, when the higher vacuum meant the lowest air flow into the engine, equating to the least fuel being metered out by the carbs. It would still work with the TDM except for the fact that a single intake cycle per throttle body means there isn't a constant measurable vacuum.