Almost nothing. I guarantee that for any non-trivial feature, you could just say:
"<non-trivial feature F> can be considered an additional feature just like any other"
And everyone will agree that's probably false. They could have written "search is almost never a trivial feature, and you should take your time to consider complications", but I suppose that wouldn't sound as a cute as a "Falsehoods Programmers Believe" list.
"<non-trivial feature F> can be considered an additional feature just like any other"
And everyone will agree that's probably false. They could have written "search is almost never a trivial feature, and you should take your time to consider complications", but I suppose that wouldn't sound as a cute as a "Falsehoods Programmers Believe" list.