Research Objectivity Standards - IB Question


I’m a bit confused regarding the ROS specifically for Investment Banking. One of the _ requirements _ states that you should not let IB department review, revise or approve any research report, however one of the recommendations states that IB personnel may review reports only to verify factual information or identify possible conflicts of interest. It seems to me that these directly oppose each other and I’m having trouble reconciling them. One of the end of chapter questions in the official CFA textbook (Question #2 Reading #3) asks about this under the assumption the example firm adheres by both the requirements and recommendations of ROS. I got this question wrong and I keep messing this concept up. Can anyone help provide more insight into this? Am I just fundamentally misunderstanding the concept here?