This didn't exist in 2000. It was created and made default on the server in OpenSSH 5. OpenSSH 5 did not make it into enterprise distros for quite some time.
There are literally tens of thousands of articles telling folks to enable ControlMaster (Multiplexing) on the client to "make ssh faster". You would be hard pressed to find a devops shop that isn't already using ControlMaster in their ssh client config. There are at least a handful of government and financial sites that set MaxSessions to 1 because they understand the risk.