If you can't trust your people, why are they your people? The consultants are going to get the story from your people anyways (even if they do their own data collection, your people are going to tell them where to look), so it's not like you're actually eliminating the bias, you're just obfuscating it.

You hire consultants when obfuscation is the point - it's not Jim from down the hall saying this, its the consultants. Sometimes there are legitimate reasons for obfuscation, but it's always some variation on "so and so needs to hear this, just not from me."