I think unlimited PTO policies only make sense with a minimum. The minimum in Australian law is 4 weeks. When I worked in Singapore I also got 4 weeks even though the labor law in Singapore technically only mandates 4 weeks.

When I work with unlimited PTO firms I will just make my intention clear from the start which is to take 4 weeks. Plus the two weeks of sick leave I am entitled to if I get sick. So max I use 6 weeks. But my sick leave accrues. LIke when I left a company I had 6 weeks of sick leave left unused and not paid, which is fine.