"The good news is that withdrawal rates are not that useful, anyway. We don't use them in financial planning. The constant withdrawals used in safe withdrawal rate analysis are inferior to variable withdrawals for sustainable spending." (8:47)
Whenever a topic like this comes up, I think many people in the conversation aren't familiar with Bill Bengan's actual study, and how humble it is. It was never meant to be a generalized pronouncement of a financial law--it is explicit about the historical context of its conclusion. And the variability is also overt, too. Bengen called 4% SAFEMAX, which then became the safe withdrawal rate. But within his dataset, a retiree in a particular year could have withdrawn as much as 10%. The 4% rule is therefore incredibly conservative, or--viewed from the other way---incredibly risky, with the risk being having a huge net worth at death, and not using that money to maximize your happiness in your life.
In this way, it is what it is--a simple model, developed by a single professional practitioner, for his own purposes as a financial planner, using a spreadsheet on his own 1990's PC. It was the beginning of answering the questions, not the be-all-and-end-all. Bengen never proposed it was that.