By "Bomb" you mean remove? Removing Carnegie, Murrubeena and Hugesdale makes the system more "Metro" how? Metros tend to have closely spaced stations (and lines!) that are within walking distances of the patrons that use them.
That section would be for express trains, ie. not a metro line (which would go via Chadstone), there's plenty of alternative surrounding stations.
The idea is to get something out of building more tunnels, rather than just building more trackwork straight up South Yarra and having no extra connectivity to show for it.
Which would be the equivalent of running the Metro Tunnel as instead an extra viaduct track pair.