"In the UK, if the door is not locked then it is not breaking and entering, and if nothing is stolen or damaged then it's not burglary."
UK , Australia and Canada all follow the Westminster system. The precedence of property theft have been established for centuries. The reason many of us were sent to Australia in the first place.
Unless the Section has been amended it would still be considered Break and Enter.
Whilst the door was unlocked, a seal (door or window or other means of access ) was broken ( in this instance Broke means simply opening the door without damage). You could not charge Break, Enter and Steal as obviously nothing of value was stolen