It's too subjective and too vague. This desire for false security is one reason HR folks feel they need to pressure managers to get the forms done. At least until their first lawsuit. You can purchase software that automates the performance appraisal process. What it does is it takes a lousy paper process, then makes it a lousy computerized process, so now we go much faster pretending we are doing something useful.
Performance appraisal is an interpersonal communication process.
Even between two people, it's often not done well. Automating the process is a waste of money and time, and HR departments that go that route are doing charitable work for the vendors of the software. It's bad enough we mechanize a human process using paper forms. Now we can take it one step further. Heck, now managers never have to speak to staff.