[katravax]

Then yes, if you limit it to the subset of software projects that can cut features and still be considered to have met the deadline, then you can meet inflexible deadlines in software projects. You've defeated technical unknowns and external dependencies with the escape hatch of "Feature x, or whatever ship-worthy part of that you can have done by date y".

In that scenario, I think you're implying that meeting a deadline is the most important metric. I consider that far more likely in periodicals than software. For the common varieties like commercial software, contract development, and in-house development, the only one likely to permit that idea is the commercial product. Contracting and in-house projects will adjust the ship date or renegotiate requirements.