Re: Since the 1990s...
I have the same direct experience. I've worked with representatives of Chinese companies that are working inside a client company. They tend to ask a LOT of detailed questions only partially related to the business at hand. I've had them demand inside confidential technical information that was only thinly related to the work we were doing. Once the Chinese rep demanded the internal schematics for a leading-edge digital chip we were supplying, something we give to no one. In one case employees started locking their desks even when away at meetings because they found items in drawers rearranged.
Their favorite response when denied the information was the same: they would look shocked and surprised (in a fake way) and tell us everyone else gave them this information. This was their stock answer.
The thing is, they were so brazen and open about it we laughed about it later. Only the naive and inexperienced would fall for it.