I have to agree with you, wanderer. I too have been troubled with this. Financial writers tend to put forward their own ideas and conclusions based on their research but rarely do they state categorically. It is usually up to the reader to determine their beliefs and investment approach based on what they have read and accepted as fact, rather than what has been proclaimed by the writer as such. It's not a science with many right or wrong answers, once you're in the right ballpark opinions vary dramatically. (I think JWR gets egged on by hocus and gets over excited as they run energetically down a blind alley leading nowhere).
As a fixed swr analysis seems fundamentally flawed. Everyone has a different asset mix and behaviour during downturns that a standard consistent approach. Psychology, fear of further losses, acting in favor of short-term losses vs long-term greater returns by holding on etc affect portfolio management during FIRE. A fixed approach & w.d. rate for all seems to be trying to bang a nail into the wrong hole. To stretch the analogy out further, I'm not even sure there is a correct hole.
I recently posted a thread discussing portfolios structured from the position of protection and funding living standards during a downmarket vs. aggressively into equities & growth ignoring the risks of a long drawn out downmarket, but sadly no one joined in.
wanderer wrote: I'm still troubled by his use of phrases like "we know" "we've proven" wrt safe withdrawal rates and the mean, standard deviation, etc. of the 'true' SWR at any given point in time. Is he still using those phrases? 3 or 4 non-overlapping data points don't constitute much 'proof' in a data-mining exercise like this, IMO.