The linked document is referring to Azure DevOps Pipelines.
There is no official macOS image for Azure virtual machines. Azure provides Mac VMs only for Azure DevOps Pipelines, which is a service for continuous integration and delivery. More details about these images can be found on this page. These VMs are co-located in the same geography as your Azure DevOps organization and always run in the US irrespective of the location of your Azure DevOps organization.
If you have questions about Azure DevOps please ask on their dedicate forum:
https://developercommunity.visualstudio.com/spaces/21/index.html
https://azure.microsoft.com/en-in/support/devops/
Hope this answers your question. Let me know if you need anymore help.
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