Honest feedback is important for growth, yes, but be ultra skeptical of peoples motives. Your manager may be downplaying your contributions to avoid having to give you a raise or to discourage you from seeking employment elsewhere.
Indeed a very valid point. Feedback has to be obtained at an individual level and it has to be given just for one purpose of constructive employee growth. I posted my comment summing up all the answers here and how i am trying to tackle these problems in my startup pleasantfish.com