loaderInfo.parameters when URLRequestMethod.POST

I have something like the following code:

var req:URLRequest = new URLRequest('child.swf');
var vars:URLVariables = new URLVariables();
vars.foo = 'bar';
vars.hello = 'world';

req.data = vars;
req.method = URLRequestMethod.GET;

ldr = new Loader();

With this, I am able to access the vars from child.swf by looking at root.loaderInfo.parameters…

but when I change URLRequestMethod.GET to URLRequestMethod.POST, I’m unable to. Any idea why, and if there’s a workaround? (sniffing via Charles makes the data look pretty much the same to me…)