The current policy is the lowest, and IELTS 4 6 also has the opportunity to immigrate.
I'm not sure how working as an assistant in a restaurant can help immigrants. According to my understanding, only the corresponding work experience of the majors listed by the government can give extra points to immigrants. For example, if you graduate from accounting major, you can get extra points if you have accounting work experience, and the extra points will vary according to the years of work experience.
Also, under the current skilled migration (EOI) policy, the number of immigrants in each major is limited every year, and then immigrants are selected from high to low until they are full, and those who are not selected will enter the next batch. So, the chances depend entirely on how high your friend's immigration score is. Naturally, the higher the better.
Only if your friend violates the law and discipline in Australia, has a serious medical problem, or his major is cancelled from the immigration list by the government, will he have a chance to reach the immigration score.