According to the translation I read, the security-related complaint in CSAC's post is mainly about Intel Management Engine. And you know what? They're right. It is a back door, and it is a security risk. Not a new or obscure one, though, and not just for China.
The risks imposed by Intel Management Engine and AMD's Platform Security Processor have been known for several CPU generations. Obviously, a lot of us are unhappy about this and would like a way to disable them.
https://support.system76.com/articles/intel-me/
https://hackaday.com/2020/06/16/disable-intels-backdoor-on-modern-hardware/
Instead, these components have been made more and more integrated with core system functionality, making the prospect of disabling them less and less practical. I fear it may take legislation to give us back control of the computers we supposedly own.