I think that Japan should not advertise only safety, but also the highest speed.
China has once been recorded the highest speed(350km) in 2011.
But, after the collision accident in Zhejiang province, China Railways decelerated its speed to 300km/h. On the other hand, Tohoku Shinkansen(High Speed Rail) raised the maximum speed to 320km/h in 2013.
So, the priority of Chinese HSR to Japanese Shinkansen is only budget.