The whole issue of SWR gets easily confused.
First, a 3.98% withdrawal works, using the default settings in FIRECalc, 95% of the time for 30 year withdrawals, while the rate drops to 3.73% for 50 years, and 3.56% for 75 years.
What makes the safe rate as low as it is is almost always what happens in the first 5-7 years of a retirement. If you are lucky enough, or your crystal ball is good enough, to retire into a rising market, then by the time your portfolio has been growing for those 5-7 years, it can withstand almost anything, and your problem will be what to do with all the money, not worrying about the withdrawal rate.
Think of this like sea turtles. If a hatchling can get past the predatory birds and get into the ocean, it's OK for the long run.