Been trying to read it all here, especially because I am about to start Retirement at age of 49. To me, this 4% rule should all be read with some common-sense. First of all, it is just a guide, not a fixed rule, and it only focus on a certain asset class, so you should look at the big picture of your Retirement-funding. In reality you would for instance:
(1) Diversify in asset classes, for instance, my early retirement income will be partially based on Rental income (this forms a basis and not directly correlated with stock market)
(2) Vary the SWR depending on how the Market performs. I keep a variation between 2 and 4% in mind. In combination with Rental income, you should plan for variation in Retirement-spending because of this. This automatically means, you should have a buffer built into your funding of your lifestyle, and if Market turns out to be bad for 5-10 years, you should be happy with a lower funding (and still enjoy life). For me this means, I will travel less around the world if the Market is really bad, and I am happy with that. I see travel as a luxury that is not necessarily needed all the time.
(3) On top of this, I keep an emergency buffer of 3 years in Cash assets. If somehow a major crash happens, i would be willing to put some of this Cash into play of Stock market
I guess, for everyone this works out differently. My main comment is : use common sense, the 4% rule is just a guide :-)