If that's the case, the responsible course of action is not to send a P3P header at all. Sending a deliberately false one to circumvent third-party cookie restrictions is simply not cool.
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.