See "Multi-Server Responses" on https://docs.jboss.org/author/display/AS71/Management+API+reference#ManagementAPIreference-responseformat:

"server-groups" => {
"groupA" => {
"serverA-1" => {
"host" => "host1",
"response" =>

{ "outcome" => "success", "result" => undefined }
},
"serverA-2" => {
"host" => "host2",
"response" => { "outcome" => "success", "result" => undefined }

}
},
....

What if on both hosts the server was named "serverA" ? The result for one would replace the result for the other.

It's important to allow hosts to re-use server names, as this makes it practical to re-use a host.xml across multiple installations; e.g. in single AMI used on many EC2 instances.