Lock Reviewer Employee Performance Feedback

I have need to let my employee login to erpnext and let them to give feedback to their colleague. But seems right now, erpnext locking the employee option to themself and let current logged in user to choose the reviewer. (which i feel not correct, how come an employee give feedback on behalf of another employee?)

How to limit/lock the reviewer to only the current logged in user?

Or anyone here can give suggestion how to handle my workflow need?