Here's the update.
After breaking the new Sailun tires in with 2000 miles on them, I measured the electric usage over a 52 mile freeway run that I made going and coming to average out the effect from any wind. The car had 265/45 tires on the front, and 275/45 tires on the back as recommended by Tesla for a 2022 MX. The total course was 104 miles, half going each way on the freeway at 65 miles/hour in self-drive. The usage dropped from 285 Wh/mi with the stock Continentals to 277 Wh/mi with the Sailun ERange tires after they were fully broken in. So the Sailun tires gave more range, but only 2.8%. It is indeed measurable, but I wouldn't call it a very meaningful difference.
Not being satisfied with only 2.8% improvement, I put the 265/45 Sailun front tires on the rear of the MX, bought 2 used rims for the MX and installed my half used 265/45 Continentals back on the front of the MX. So, this made the MX with a square tire pattern, 265/45 on all four tires. I just got home after running the same exact freeway course that I used in paragraph one, above. The electric usage dropped to from 277Wh/mi to 269 Wh/mi, for another 2.8% improvement in range. Neither of these changes produced a meaningful improvement by itself, and the 5.6% combined improvement seems barely meaningful.
I'll leave the car with this configuration until I need to tow my boat again, and then put the bigger tires back on the car.