The title is misleading. These trains will have an actual operating speed of 360kph (224mph). In contrast, the fastest shinkansen trains (hayabusa) currently operate at 320 kph. It's still a solid speed increase but not as ground breaking.
If they use the technology, they’ll be saving billions of riders many hours a year.
According to China Railway, from 300 km/h to 350 km/h will increase resistance by 40%, power consumption by more than 50%.
China already has trains with similar speed.
If generation gets cleaner and cheaper that's less relevant. We only know one way to power aircraft and CO2 is intrinsic to it.