and it was a requirement at the time that such 'colonial flags' must include the Union flag to indicate the status of the dominion as 'an imperial dominion of the British Empire'.
Rubbish. This was not a requirement of the competition. There were no restrictions on what elements the flag should consist of.
The appeal here made is to the artistic imagination, and designing skills of the seven colonies. It ought to have the effect of giving birth to a Flag which will hold a proud and long enduring place amongst the Flags of the civilized world.