Example 1: I want to remarket to visitors who saw a certain Optimize variation in Google Ads.
Example 2: I created an audience in Analytics 360 for use in Optimize, and I want to share it with Google Ads.
Audiences can be created (and shared with Google Ads) based on whether users were in a particular experiment or variant. Similar to above, audiences created in Analytics 360 for use in Optimize can be copied and shared to other products.