Speaking truth to power is rarely easy. Some leaders can take genuine feedback others cannot. Until you have a good pulse on the situation, is it really surprising most people default to inauthentic critiques?
This is why I'm very skeptical on the use of 1-on-1 meetings with management as a means to keep a finger on what's going well or badly in an organization.
If someone is OK with telling management things they don't want to hear, they'll tell management those things regardless of 1-on-1s.