It shall be an unfair practice for any insurer to rely solely on another insurer's denial, cancellation, or nonrenewal of insurance to support a denial or termination of coverage. In every case, an insurer must go behind another insurer's action and make its own independent decision on the merits. This section does not prohibit an insurer from denying a binder pending its evaluation of another insurer's action, and does not apply to an insurer-reinsurer relationship.