I don't think that's the way it works out in practice. The fact of the matter is that deadlines are missed all the time. In many cases, there is no such thing as 100% certainty that you'll hit a "deadline"--there are always circumstances outside your control (global pandemics anyone?). There's just some implicit confidence threshold or other assumptions lurking around that probably need to be communicated. Do you want three 9s of confidence? Five 9s? Those things are very different and the cost to actually achieve the latter can often be prohibitive. Everyone benefits if we make explicit our pre-conceived idea of precisely what "cannot exceed" means.