The goal is to "grow" an AI through reinforcement learning and other techniques that are broadly applicable outside starcraft. The existing rules based systems in the game A) are extremely Starcraft specific and the methods have comparatively limited utility outside video game AI, B) unlikely to be scalable to fairly beat a professional human (which introduces too much variability to capture reliably into rules)

The built in ai is scripted whereas they’re trying to teach agents to learn the game from scratch with some sort of reward-based/machine learning approach.

still, why not use machine learning to tweak the script instead of starting from scratch.