I have several years of experience in giving mock interviews. I learn a little about the candidate, give an interview which showcases both qualitative and quantitative skills, and at the end of the case, provide detailed, tactical, and constructive feedback.
Several of my peers have directly credited my feedback with obtaining an MBB offer. I frequently received feedback that my comments were the most actionable and detailed of any practice case partner my interviewees had worked with. I also have a 95% success rate in assessing whether a candidate will get an MBB offer and can provide an assessment as to whether your casing ability will pass the test.