When I ran numbers through Vanguard's simulator, it's answers stayed the same when I lowered or increased stock allocation from the standard 60/40. Maybe Vanguard is using out of date performance numbers for bonds?
With treasuries all paying 0% to 1%, I think replacing the "bond" allocation with "cash" in simulators is appropriate. Using various mixes of stocks and cash over 40 years (retire early!), and withdrawing 4%:
60% stock / 40% cash : have >$0 left 79%
80/20 and 90/10 both give 82% of having >$0 left.
My guess is secondcor521's use of FIREcalc is probably more accurate, but at least you can see Vanguard's numbers in case it matters.