Yes! I can’t believe I don’t see this repeated in one form or another more often. Fallacies are a bit like prions in that they tend to force a cascade of fallacies to derive from them, and one of my favorite debate tactics is the thought experiment, “Let’s assume your entire premise is true. How might this contradict your position?”
Usually the list is longer than my own arguments.
I think there’s a less perplexing answer: that at some level we realize that our performance is not 100% reliable, and we should shift down our estimate by an intuitive standard deviation of sorts. That way, we can under-perform in this specific case, and won’t have to deal with the group dynamics of someone else’s horrible disappointment because they were counting on you doing your part as well as you said you could.