https://www.cpf.gov.sg/Members/Schemes/schemes/retirement/withdrawals-of-cpf-savings-from-55
It is very clearly stated in CPF website that no top-up moneys are eligible for lump sum withdrawal at age 55.
All top-ups and their accrued interest turn eligible for lump sum pay-outs only at age 65.
So anyone depositing voluntary top-up should be highly aware that it transforms into payout only from age 65.
This arrangement is logical because if a 55 yo is so "desperate" as to insist on a lump-sum withdrawal of top-up moneys at age 55, instead of waiting another 10 years to receive it at age 65, he is probably not in the best state/shape for real retirement at age 55.