Was the preference for 9.2-inch post-Hawkins cruisers based only on earlier armoured-cruiser practice?
Short answerNo; a suitable 9.2-inch gun was becoming available at the relevant time.
NotesA suitable 9.2-inch gun was becoming available at the relevant time, which drives the preference for that calibre in a post-Hawkins cruiser. Earlier armoured-cruiser practice is insufficient by itself to explain the choice. Surviving examples in Australia are mentioned as a way to identify the gun being discussed. The passage links cruiser armament to the availability of an actual weapon at the moment of design.