[trekky1700]

How are death camps, the specific targeting of civilians, medical experimentation on detainees, burying prisoners alive and even cannibalism covered under "war of conquest". When does it become genocide? How is it any different (if not worse for its unparalleled scale) than what the Nazis did?

They didn't just target Chinese civilians, they targeted the civilians of every nation they invaded. This includes the British civilians in Singapore and Hong Kong who were sent to ghettos and labour camps, few of who survived. And this was the "preferential" treatment the Brits got. The Chinese and other Asians got far, far worse.