I think what it means is that coding is difficult but predictable — in the sense that, you can solve it by throwing enough money at it. Figuring out what to build in a way that actually leads to product-market fit, on the other hand, is something you cannot solve just by throwing money at it. So in this frame, coding becomes 'the easy part' — not because it's truly easy, but because it can be solved relatively straightforwardly with resources