> This is pure speculation, but I'm guessing they were working on ensuring that the ML models built by Twitter to do things like content moderation, tweet promotion, identifying trending hash tags, customer service help, and more were behaving in an ethical manner.

Sure, but this is just a feature of the product in question, so if you have some metrics to measure such outcomes then the product developers themselves can do this checking as part of their development process. I'm not sure why this would need to be a separate division. Presumably Tesla's autonomous driving developers are also creating metrics to ensure they don't run over dogs and children, they don't need a separate ethics division to tell them this is important.