If you retire super early (like 30s and 40s), a small pension in your 60s doesn't actually make much of a difference in the SWR (less than 20 bp). You also have a shortened working timeframe so that could be a lot of years with $0 SS earnings.The whole withdrawal rate discussion frustrates me because it ignores annuities like SS and pensions; a higher WR would work if you had SS and/or pension (presuming you cut your WR when you start getting those annuities, which only seems logical). Or, if you added the present value of your annuities to your current assets, then WR would be apples-to-apples (but then small changes in the inflation assumption can change the result).
That said, most retirement calculators don't take into account human flexibility. I doubt most reasonable folk would continue increasing their withdrawals by CPI when their portfolio is getting hammered. One caveat is you'll need plenty of give in the budget.