Because you will have an understanding of the complete system. Your domain and the code. This means that you can be more creative with it and also get yourself out of a mess if it occurs (which it will).

From what I have seen AI doesn't understand the code. But even if you argue that it does understand the code it definitely doesn't understand the domain because it's only input channel is a stream of text and you didn't even type in a "full" text representation of the domain.

So you remain the only thing that can understand the whole system. If your competitor has no one (or no team) who can put together a full understanding of the system then you will have an advantage.