My experience has generally been that, even if a leadership level person is being sincere when they say they want honest feedback and it is safe to offer it, the junior level person they are meeting with doesn't believe it. (An economist would call this an example of the "market for lemons" problem.) That is a big reason why outside consultants can break the ice on something like this, as the article describes, where internal conversations can't: the consultant can credibly promise that honest feedback won't adversely affect the speaker (the obvious way to do that is to not attribute anything to any particular person when the consultant reports to leadership), so they have a shot at actually getting the honest feedback that is needed to get to a solution to the problem.