It's not that Japanese people are hiding their history. If there are clear evidences that are not flawed and could not be denied, they will not deny, but admit and apologize. For example, there was the famous Korean sexual slavery issue coined by Seiji Yoshida that later he and Asahi Shimbun admitted it was a complete fiction. This revealed that the comfort women issue was not about slavery but prostitution.

Why do you apologize for the thing if it wasn't true? The thing which is making complicating is that the Chinese government is promoting hatred towards the Japanese government as a propaganda and is exaggerating the results.

Do you really believe the claims of the country which has the Great Firewall? Do you really believe the country which the government is officially producing anti Japanese movies? Do you believe the country which hides the Tiananmen Square Incident and the ongoing killings of the people in Tibet and Xinjiang?

There are suspicions of the claims and the numbers coming from such country.