In the rest of the World Fly Runway Heading means fly the Track with drift correction.
Simple? Ya joking surely? Get with the program, you POMs (and the rest), Heading is Heading and Track is Track!
To be fair, Nitpicker, if the Aussies want you to maintain runway track after takeoff eg night/IMC, ATC will ordinarily say "Track 016 degrees, Clear For Takeoff". Absolutely no doubt about what they want with that.
The only time you would pull HDG would be if you needed to cancel the SID and turn.
Or if the EO procedure called for Straight Ahead and the SID required a turn...