Currently the User Scope does not automatically update based on the Active Directory deletions. If an OU/group is removed from Active Directory it is still referenced as being "in scope" in Password Manager.
An enhancement request (TF00785540) has been created detailing the feature above.
The product team will evaluate the request and this feature may become available on a future release of the product.
Please refer to this article for updates or contact support referencing the Enhancement Request ID: TF00785540.