Route 53 - ConflictingDomainExists - subdomains with (White-Labeled) Reusable Delegation set

Trying to set up a sub domain of a domain this is 1) created with a Reusable Delegation set, that also host the white label DNS records.

The error I get is:

Error: error creating Route53 Hosted Zone: ConflictingDomainExists: Cannot create hosted zone with DelegationSetId DelegationSetId:N07332301DF5CDCEBAHPP as the DNSName <my sub domain>. conflicts with existing ones sharing the delegation set
       status code: 400,

AWS documentation on these concepts is very this on the ground.

To quote:

Create a public hosted zone: Two hosted zones that have the same name or that have a parent/child relationship (example.com and test.example.com) can't have any common name servers. You tried to create a hosted zone that has the same name as an existing hosted zone or that's the parent or child of an existing hosted zone, and you specified a delegation set that shares one or more name servers with the existing hosted zone. For more information, see CreateReusableDelegationSet.

There is not much on this in google land but did find this old forums post to explain the likely issue but don't know best approach to resolve.

It would be great is AWS would update documentation to explain how to do this ?