I'm not sure if I have an odd truck, but my truck upshifts all the way to 5th gear when in S6 and the ECT button is on. 2018 TRD off roadV6. Upshifts from a stop come on a regular basis, and perhaps 5 mph to 8 mph higher than the truck without ECT on and in S6 mode. The only hold out is when the truck shifts into S6, and in all of my driving in this mode, it will not happen under 56 mph with a light throttle on a flat road, or as close to flat as possible. Upshift into S6 happens just under 60 mph if you have any pressure on the throttle, but it does upshift into S6 using the ECT button.