Has this thing ever worked in any version from 4.x through 9.x?

Below is the content from SAG pdfs

In general, if a remote server is not available when a request is made, and the remote
server is not part of a cluster, Integration Server will use the retry server specified in the
alias definition for the remote server.
If the requested remote server is part of a cluster, Integration Server will a?empt to use
the next Integration Server in the cluster until one is found. If no available Integration
Server is found in the cluster, Integration Server will use the retry server specified in the
alias definition for the remote server.
In cases where a client calls the pub.remote:invoke to run a service on a remote server that is
part of a cluster, it is possible to modify the default behavior by using the $clusterRetry .
This parameter controls whether the service will try other Integration Servers in the
cluster. When this parameter is set to true, the service will try other Integration Servers
in the cluster. If none are found, the service will try the retry server specified in the
remote server alias definition. When this parameter is set to false, the service does not
try other Integration Servers in the cluster. Instead, it will try the retry server specified in
the alias definition.