Comment by __MatrixMan__

I don't think it is, because the intro gets it wrong. If a problem's time or space complexity increases from O(n^2) to O(n^3) there's nothing necessarily novel about that, it's just... more.

Complicated on the other hand, involves the addition of one or more complicating factors beyond just "the problem is big". It's a qualitative thing, like maybe nobody has built adequate tools for the problem domain, or maybe you don't even know if the solution is possible until you've already invested quite a lot towards that solution. Or maybe you have to simultaneously put on this song and dance regarding story points and show continual progress even though you have not yet found a continuous path from where you are to your goal.

Climate change is both, doing your taxes is (typically) merely complex. As for complicated-but-not-complex, that's like realizing that you don't have your wallet after you've already ordered your food: qualitatively messy, quantitatively simple.

To put it differently, complicated is about the number of different domains you have to consider, complex is about--given some domain--how difficult the consideration in that domain are.

Perhaps the author's usage is common enough in certain audiences, but it's not consistent with how we discuss computational complexity. Which is a shame since they are talking about solving problems with computers.