From what i know cpf interest is compounded while ssb is simple one (i forgot the actual term, rate * invested amt). By right compunded interest give better result than simple one for the same rate over time.

Source: https://www.cpf.gov.sg/member/faq/growing-your-savings/cpf-interest-rates/how-is-my-cpf-interest-computed-and-credited-into-my-accounts -> first paragrah: compounded annually.

Using this calc https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator $1000 with 4% compounded interest gives you $3,243.40 1,000 with simple 4% rate gives you $2,200