Most HDB owners refinance to lower their monthly repayment, not to unlock cash. Because MSR (30% of gross income) applies to HDB and EC loans, the packages that work best for HDB refinancing aren't always the same ones that top the general rate tables.
MSR is usually the binding constraint, even when TDSR would allow more.
Some banks still factor MSR into refinancing decisions for HDB loans, even though TDSR itself doesn't apply to a like-for-like refinance.
CPF usage rules and the HDB loan vs. bank loan distinction affect which packages are available to you.
Current lock-in status, CPF accrued interest implications, valuation requirements, and the full set of bank packages eligible for HDB properties — then translate it into one number: what you'd save per month and over the lock-in period.