Which isn't an upgrade of the battery for the model. As was done for the Volt, Spark EV, and gen1 Prius.
I would be happy the charge button is simplified. I had to learn not to get into charge mode by holding button down too long. As it is in all black on the dash and low to the side, I find it hard to see the button unless I stare at the area for a second.
And why is that? A Li-on battery performs better than a NiMH battery, and it is lighter. It is not to mention that it is much more durable. As far as I know, all NiMH Gen 4 batteries were upgraded to Li-ion in later model years if that’s where you are mistaken.
One possibility for charge mode being removed from US/CA Gen 5s could be how many owners here and possibly other Toyota forums bashed it so badly as utterly useless and worse. @john1701a did a few videos showing how Hybrid Assistant tracked the mode in action. I used DrPrius on an empty stretch of a Parkway and noticed a few interesting aspects of how charge mode works, myself. Especially between 20 and 55 mph. Then there are the differences between holding a steady speed on the " flat " compared to what the gauge shows during acceleration or deceleration. Spiking up from the Gen 4s average " steady speed on the flat speed of 20mph " charge rate of 20 Amps to 40 Amps for short periods. Then there are the hills and valleys behavior where the charge level bounces all around the Amp gauge continuously.
