That’s incorrect.
25% of your pension pot is not subject to tax, the remaining 75% is, regardless of when you choose to take it, and how much of it you choose to take.
This isn't entirely accurate. One's income is subject to tax, not the source of the income. Whether or not one pays tax on the 75% depends on one's total annual, taxable, income.
In my direct experience one can take:
A tax free sum up to 25% of the fund value.
Annually one can drawdown, take an income, which is free of tax (note phrase, this is NOT tax free) up to the Personal Allowance for that year. This payment is classed as PAYE and tax is deducted at source. The payee then reclaims the tax from HMRC.
This is precisely how I have funded my retirement without paying any income tax. When I began to receive the State Pension I reduced the drawdown to the balance between the State Pension and the tax threshold. My State Pension is now above the threshold so I've stopped the drawdown.
In other words any payment taken from the 75% is added to one's taxable income. It's one's threshold that determines if that income is taxed or not.