What you are missing is that 4% of any principle is enough to start at and will last 30 years, adjusted annually for inflation.
No, what we are saying is that the reason why 4% works as often as it does (93% of the time) is that when the crash happens, often the portfolio has built up enough that your WR is actually below 4% by that point, even though you've adjusted for inflation, because it outgrew inflation, and that outgrowing allows it to last.
Let me make up numbers to illustrate the point.
Lets say a crash happens at year X.
If you FIRE one year before that (at X-1) at 4% WR, you probably won't make it the 30 years. You'll be in the small handful of failure cases. Ditto at X-2. Maybe at X-3.. But maybe at X-4, X-5, etc. your portfolio has gained enough from those 4-5 years that when the crash happens at X, you last through it (in a way you wouldn't if you FIRE'd only 1 year before, at X-1).
But if you do your plan to reset every year, you're constantly risking a crash happening next. Thus -- like Eric said -- you're increasing your sequence of returns risk.
There
are failure cases with the 4% rule, and by constantly resetting and potentially inflating your spending to 4% (but never reducing), you're vastly increasing your chance of being a failure case, because no longer do you have to get past the first few years of FIRE, but you have to continually do it.