http://www.immi.gov.au/skilled/g ... ibility-english.htm
What is the International English Language Testing System (IELTS)?
The IELTS is a test designed to assess an applicant's English language ability. It has an academic test and a general training test – you need only take the general training test unless otherwise advised by your skills assessing authority.
The immigration authority reserves a right not to recognize your academic IELTS result if you only have the academic result. There is nothing saying that the academic IELTS be a legal/valid substitute. I guess an applicant would not want to argue with the immigration department regarding a "point of law."