The response to "what about volatility" is not really right. Volatility makes a much bigger difference than the article admits - the reason FIRE proponents come up with a similar number is because they started with a much higher number. They are using US-only historical returns, which average around 7% (inflation-adjusted), not 5%, and the safe withdrawal rate is typically quoted as 3.5%-4%. So in order to be safe, you have to cut the return rate in half or so.
There's probably an argument to be made that this is still too aggressive, because US historical returns feels like cherrypicking - they're much better than international returns, and there doesn't seem to be a good argument for expecting that to continue.
That said - how many 80% drops are there? If your criteria for safety is "will have enough money to last forever even if the great depression hits the second I retire", you might be a bit too conservative - it's hard to imagine another great depression at all, given the Fed's recent history of propping up the market in crashes, let alone at the worst possible time. You'll never be able to take chances on anything with requirements like that.