With T266029 in, we still need to represent alerts in Dialogs.
Re-citing from Github:
Alerts are an important part of a platform and user experience that helps maintain consistency.
Currently, the Style Guide doesn't contain any components for Alerts. Alerts is a basic component that should be added.
OOUI provides a few “simple” dialogs that are falling in this category, “Quick alert” and “Quick prompt” to name the least.