Informal answer: China has always hacked. Furthermore, this happens everywhere, and human nature does not suggest China being an exception.
China became a member of the World Intellectual Property Organization (WIPO) in 1980. This indicates the timestamp when intellectual property officially began to be seen as such.
The former Democrat administration followed the idea of intercontinental cooperation:
Finally, we’re taking more steps to expand the connections between our two peoples.
As this speech does not address piracy at all, in spite of naming differences, it can be assumed that the topic was intentionally left out.