Konfirmed at this source too:

POSSIBLE SPOILER ALERT!

Rated R18+ in Australia, for the following reasons: Themes (Strong impact), Violence (High impact), Language (Strong impact), Sex (Moderate impact). I do NOT know what these mean in Australia, so sex could just mean some kind of sex appeal or that there will somehow be sex despite no nudity. The film will not have drugs or nudity. Src: https://www.classification.gov.au/titles/mortal-kombat-17