Hi Ketan,
I'm sorry for the late reply.
This is used to define custom logic on what constitutes an approved review request. Then, client-side, APIs can check the "approved" flag on a review request's payload, which will reflect the result of that calculation. This is the recommended approach at this time, as it's faster, future-proof (working with things like repository pre-commit hooks that check for this state), and can do things like directly query the database or a central configuration for the information you need.
Christian