It is significantly easier to micro-manage an AI than a suite of junior developers. The AI doesn't replace a principal engineer, it's replacing junior and weaker senior developers who need stories broken down extremely concisely to be able to get anything done. The time it takes to break down a story such that a junior through weak senior developers can pick it up and execute it well would have the AI already done with testing built around it.
It is significantly easier to micro-manage an AI than a suite of junior developers. The AI doesn't replace a principal engineer, it's replacing junior and weaker senior developers who need stories broken down extremely concisely to be able to get anything done. The time it takes to break down a story such that a junior through weak senior developers can pick it up and execute it well would have the AI already done with testing built around it.