Why SWR at all, certainly not the only game in town? The originators specifically recommended that no one should just follow SWR come what may.
You can always do % of remaining portfolio (presumably increasing the % as you get much older) with a cash reserve to smooth annual income, or take out distributions only (forever, or until much later in the plan).
I will probably use % of remaining portfolio (with a cash reserve) for the first 15-20 years, and then I may go to SWR. There is no universal bulletproof plan (not that the OP claimed there is), not even cash only, not annuities/pension only, none...