Sure. Though of course that means some functionality will be broken for all IE users with default privacy settings.
A faked P3P header breaks IE's privacy settings in a nonfixable manner.
Not for the average user. The user who uses the default web browser. The user who uses IE.
I suspect you're right and the uptake isn't what they wanted, but that's not really a valid reason for them to work against the browser settings designed to protect a user's privacy.