AE are meant to reduce the chances of vomiting,that's why it's recommended.
But also having AE doesn't mean you'll not vomiting,Some members reported to have vomited even after using AE.
Thats why the Stan regime recommends to have a backup SN glass just incase you vomit to increase chances of successful ctb.
You can use the search options to peruse the list of goodbye threads to see different experiences from different members who successfully ctb and those who failed.