Here’s the documentation which gets to the heart of what you are asking:
“Both the source group and the target group are locked during the move operation. Write and delete operations are blocked on the resource groups until the move completes. This lock means you can't add, update, or delete resources in the resource groups. It doesn't mean the resources are frozen. For example, if you move a SQL Server and its database to a new resource group, an application that uses the database experiences no downtime. It can still read and write to the database. The lock can last for a maximum of four hours, but most moves complete in much less time.
Moving a resource only moves it to a new resource group or subscription. It doesn't change the location of the resource.”
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