Well that's a good decision. I doubt it covers client-side redirects, but still good for like 95% of cases.
People do still allow 3rd party images/links on websites. Much less common in typical software, but it does happen.
Why would it? Someone has to go and write the code to do it and the spec doesn't look like it covers them.
Playing with window.location and meta redirects in jsfiddle, they both seem to lose cross-site context when I link to them.