Are you seriously suggesting Facebook use it's employee's private account data as part of hiring & performance management?
No. This is explicitly illegal in some states.
https://www.cnet.com/news/six-states-outlaw-employer-snoopin...
Also I read through the text of those laws and they all specifically say that they are not limiting the employers right to monitor their own systems in any way. So Facebook looking up how their employees use Facebook would be completely fine under those laws.