Earlier quoted context omitted.
It would be funny if the DoD is attached to waterfall still. The entire organizing principle of modern US warfare is as fast and adaptive a battlefield loop as possible for: get information -> adapt strategy -> deliver orders. I believe it goes back to Napoleon, who basically conquered all of Europe using those principles and superior organization.
The whole F-35 is a waterfall project gone horribly, horribly wrong, then eventually shipping without most problems being addressed.
Now; aircraft are very different than software. You don't go and manufacture 1000 birds based on a partially completed design. So there's that.
The other important thing to note is the F-35 concept was meant to address the sharply rising costs of building warplanes. By taking advantage of "economies of scale" in manufacturing, to build a multi-purpose plane that all three services could use. (so instead of building say; 100 of one design for the USAF, 100 of a completely different design for the Navy, 100 of a third design for the Marines, they'd build 300 planes - but manufacture variants off the same assembly line.) Adding to that scale was the baked-in "deal" to get NATO partners to commit to buying these planes as well. In that regard, it was kind of a stunning success (that they're actually serviceable; even if all three variants have shortcomings due to engineering trade-offs made for this manufacturing flexibility). At the end of the day, there were flaws that arose in the concept; like, the main central titanium bulkhead, which turned out to be FAR more costly to manufacture than was revealed when they built the prototypes. They just kind of "hoped" that the process for that part would end up being cheaper when scaled. And it wasn't cheaper-enough.
This makes is sufficiently different to the software development process discussion, that I think it's really an apples-to-oranges comparison.