mention update op is required and all MDB resources support import

Author: oarbusi

cfn-resources/README.md

@@ -62,13 +62,15 @@ Note these are also hosted on AWS CloudFormation Public Registry under Third Par
 
 ## Resource Import Operations
 
-MongoDB Atlas AWS CloudFormation resources support the import operation, allowing you to bring existing Atlas resources under CloudFormation management. When importing resources, please consider the following:
+All MongoDB Atlas AWS CloudFormation resources support the import operation, allowing you to bring existing Atlas resources under CloudFormation management. When importing resources, please consider the following:
 
 ### Import Requirements and Considerations
 
 1. **DeletionPolicy Attribute**: Your resource template must include the [DeletionPolicy](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-attribute-deletionpolicy.html) attribute in order to specify what happens to the resource when it is removed from the stack.
 
-2. **Outputs Restrictions**: As part of the import operation, you cannot modify or add [Outputs](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/outputs-section-structure.html) to the template. However, you can add outputs after the import is complete.
+2. **UPDATE Operation Required**: The import operation executes the UPDATE operation behind the scenes. Therefore, UPDATE functionality must be properly implemented for the resource type to support import.
+
+3. **Outputs Restrictions**: As part of the import operation, you cannot modify or add [Outputs](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/outputs-section-structure.html) to the template. However, you can add outputs after the import is complete.
 
 For more details, refer to the [official AWS Resource Import documentation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/resource-import.html).