More evidence in support of the central governor theory. It's not about the carbs, it's about the brain getting the "we got carbs" signal, which leads to increased effort.

Possibly, yes. Perhaps the next steps will be to wrap the tongue completely or oral dam as a control.

Perhaps it's an evolutionary biological optimization (like anticipatory salivation) to release caloric / nutritional reserves sooner rather than wait until a digestion pathway is completed.

And I wonder if sweet taste stimulation by any or all artificial sweeteners also does something similar.