I find the juxtaposition of these two points to be... puzzling. Retirement funds aren't meant to be day traded, but drawn down in a boring and predictable manner (even better if you can just pull out dividends and leave the shares untouched); there's generally no reason to worry about the exact time in which a withdrawal is executed unless you have a crystal ball and are trying to time the market, which seems like behavior that is at odds with a sober and low risk mindset. To see that coupled with an argument about having no stock exposure because the risk is too great...
I guess that even if I have a notional number I want to hit, it's all based on probabilities. If you can exceed that number, or stretch your withdrawals a bit, you insulate yourself from longevity risk that wasn't accounted for by your original model. There's also some evidence that some modest stock exposure can actually reduce your volatility, as bond prices have historically moved opposite stocks (this assumption has been tested in recent years with the zero rate bound, though, so it may not be as relevant today). *Shrugs* to each his own.