I am reading this link from Google cloud- https://cloud.google.com/composer/docs/concepts/overview
It says "Cloud Composer 2 environments have a zonal Airflow Metadata DB and a regional Airflow scheduling & execution layer. Airflow schedulers, workers and web servers run in the Airflow execution layer."
If Airflow Metadata DB is not replicated across multi region, then even though execution layer is multi regional.. In case of Disaster, My composer instance in the DR region will be dead. What is the point of providing a multi regional execution layer, but zonal Metadata DB?
Cloud Composer 2 has an overview for Disaster recovery that might give you insights in your inquiry.
In your case I believe you are looking for high availability DR architecture.
When you run production workloads on Google Cloud, you might use a globally distributed system so that if something goes wrong in one region, the application continues to provide service even if it's less widely available. In essence, that application invokes its DR plan.
The document provides details about disaster recovery planning, requirements and what Google has to offer when it comes to DR.