ECS already makes it a hundred times easier for me to conceptualize game mechanics, modify and extend them. Giving AI the ability the ability to create data separate from systems that use them will make it much easier for it to build a game. I don't believe for a second it will be able to write functioning object-oriented game code for example. It will likely be best if it avoided coding via a text-based language altogether, and use visual scripting or another system based on chaining logic blocks together. But that still counts as the "system" part of ECS.