chore(iam): clarify policy docs (#29416)

Closes #29398. 

@abdulkadirdere – Let me know if this clarifies things.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk-lib/aws-iam/lib/policy.ts

@@ -79,7 +79,8 @@ export interface PolicyProps {
    * creating invalid--and hence undeployable--CloudFormation templates.
    *
    * In cases where you know the policy must be created and it is actually
-   * an error if no statements have been added to it, you can set this to `true`.
+   * an error if no statements have been added to it or it remains unattached to
+   * an IAM identity, you can set this to `true`.
    *
    * @default false
    */
@@ -96,9 +97,9 @@ export interface PolicyProps {
 }
 
 /**
- * The AWS::IAM::Policy resource associates an IAM policy with IAM users, roles,
- * or groups. For more information about IAM policies, see [Overview of IAM
- * Policies](http://docs.aws.amazon.com/IAM/latest/UserGuide/policies_overview.html)
+ * The AWS::IAM::Policy resource associates an [inline](https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies.html#inline)
+ * IAM policy with IAM users, roles, or groups. For more information about IAM policies, see
+ * [Overview of IAM Policies](http://docs.aws.amazon.com/IAM/latest/UserGuide/policies_overview.html)
  * in the IAM User Guide guide.
  */
 export class Policy extends Resource implements IPolicy, IGrantable {