Aussie here. Using Safari/iOS with an ad-blocker, tested un-logged-in Google, Bing and DDG. Search was “naked women porn”. Only Bing asked via a pop-up whether I was over 18, with options “Agree” or “Disagree”. No other inputs required.
One piece of anecdata. Not particularly scientific. TBH the submitter (or anyone else) can use a VPN with an Australian exit node to test this for themselves.