Iv seen pinoys working in Australia that came from Singapore....I think they have triple citizenship.
Nothing wrong if they have 3 citizenship. It's called having an insurance policy in case Country A goes to the shitter, they can always legally move to Country B. If Country B goes to the gutter, they can always move to Country C.
Moreover if the Pinoys you mentioned have Aussie citizenship, they are also free to move to NZ permanently if OZ goes to the shitter. In essence, they have 4 countries to choose from to legally reside permanently; namely, Philippines, Singapore, OZ, NZ.
People should treat their passports like credit cards. The more passports and credit cards issued in different countries, the better is their insurance policy.