You don't get a free pass because you're following a W3C standard. The way P3P is implemented in IE made web developers lives harder in exchange for virtually no additional privacy protections to users.
The point of the standards process is so that we don't have multiple competing/incompatible/ambiguous header-based privacy policies. But that's not the problem here. There aren't any notable competing privacy headers because the whole approach is flawed.
Are you going to say the same thing about the FileSystem API, Dart, and NaCl? Google is probably the worst browser vendor when it comes to having competing implementations of their proprietary features.
The point of the standards process is so that we don't have multiple competing/incompatible/ambiguous header-based privacy policies. But that's not the problem here. There aren't any notable competing privacy headers because the whole approach is flawed.