Read my post. I reset the computer AVG MPG calculation once after driving the first 80 miles with Sport mode on the way back to San Jose. Since the rest 275 miles was without Sport mode, hence the computer MPG calculation after the reset got higher. The manual calculation is for the entire 355-mile trip, with and without Sport mode.
I get it now. One thing I overlooked was that in Sport mode doing 70+ MPH revving high in 4th. or 5th. without hitting overdrive you logged you logged 36 MPGs over those 80 miles. That is certainly a big factor. As an aside, it is quite remarkable you would see those MPGs without hitting overdrive in a vehicle rated 40 MPGs highway along with the other quite remarkable readings.
I would, however, resist making generalizations such as this:
"I’m totally convinced turning the TCS off on Mazda vehicles somehow makes the engine peppier and more efficient (or less unnecessary braking by TCS), hence improves gas mileage significantly!"
In limited testing, my vehicle shows no noticeable difference per the MPG display, in one instance up to 40 miles on country roads with TCS off showing no meaningful difference. Someday on a road trip I can try a tankful with TCF OFF to see if I get better than the 31-33 MPG manual calculations I've seen in the past on straight-up expressway driving. I'm not holding my breath.
Also, I would resist making Mazda generalizations about the accuracy of the MPG display. I've experienced the contrary on a couple of occasions where it was overstated meaningfully when compared to a manual calculation--3/4 tank, same pump, no overfill past auto shut off. You will find other posters who share that experience. One car is not another car, even the same year and drive train.
As an FYI, my vehicle does in fact kick into 6th. gear overdrive in Sport mode when I reach a steady 70 MPH. I happened to be out on expressway today and tested this. In fact, it was settling in right around 2,500 RPMs in all four combinations of TCS off or on with Sport on or off. The only noticeable difference is that in Sport mode it resisted cylinder deactivation whether TCS was off or on.