"Also, let's not forget that 4% is extremely conservative for those who are in fact able and willing to modulate their spending significantly and/or generate income. "
Yep, but then, getting back to the first post of this thread, it's not a "safe" (as in SWR) FIRE any more - it's more of a conditional FIRE. As you say, that sort of condition may be completely to someone's tastes, if it means the difference between working away for the man versus having a pleasant-ish part-time blogging job at a pinch.
"Each person must assess their own risk, and honestly, that risk has so little to do with the math and SO MUCH to do with how happy they are in the PRESENT."
Another very good observation. Whether you want 90%, 99%, or 99.9% certainty with your SWR probably has a lot to do with how badly you want to quit your job in the present.
There is no absolutely safe withdrawal rate though, and 4% is very safe for the vast, overwhelming majority of cases.
Safe is still and always will be a relative statement. A 4% WR is reasonable to consider safe unless an unlikely and very particular sequence of events occurs and the person involved is somehow unable to react reasonably to those circumstances.
Even Big ERN himself in a Choose FI podcasts said that 4% is more than conservative enough if you account for basic human behaviour, such as defining the annual spend amount with ample buffer/fat in it, as well as the natural instinct to cut costs if the person's nest egg takes a beating.
Say we have imaginary person A who plans to withdraw exactly 4%+inflation exactly annually and has no buffer in their budget at all. The unexpected realities of life are more likely to fuck them up than SORR ever will.
Adding buffer to a budget and lowering WR amount to basically the exact same thing conceptually in the end.
The set withdrawal rate of a plan is virtually irrelevant compared to what rationale makes up the defined "annual spend". The inputs matter far more than the outputs when it comes to these simulations, and those inputs are based on some pretty hand-wavy arithmetic.
If we account for actual normal human behaviour, such as padding in budgets and an instinct to cut spending when the 'stache drops significantly in value, then the 4% rule is about as safe as it gets, and working more to generate diminishing benefit is excessive for anyone who isn't delighted to stay at their job.
You simply CANNOT look at these models in a vacuum as if they actually model anything even remotely close to realistic spending patterns.
If someone looks at their savings amount, looks at the amount that 4% would provide and thinks "oh, that's plenty!" then they will probably be fine. If they cringe and think "Yikes! I think I can survive on that..." then it's more risky.
Nothing in life is 100% safe.