Yes this is true. I worked for two years as a casual with conditional registration, as my degree is also 3 years.
However, I´m now enrolled on a Special Education Masters to enable me to apply for a 189/190 visa to return permanently. Primary Teachers are not on the SOL so if you are going to do another year of study I wouldn´t do it in Primary Ed, as you still won´t qualify then. I´m appyling as an SEN teacher. Unless, you do the Masters in Australia.