The sso domain is different the the fqdn of the host though, that was the point I was trying to make. In 6.7  you can have external platform service controllers that handle the SSO domain, is the vsphere.local in sso administrator login(administrator@vsphere.local). You would point the vcenter server at these, so if you repoint the vcenter from a set of PSCs or to a new embedded psc in another vcenter. In this case all dns entries are all the same . Here is an article with an example

https://virtualtassie.com/2018/vcenter-6-7-cross-sso-domain-repointing/

the OP wants to repoint from company A to company B. In this case the vcenter fqdn and ip are staying the same, its just the vcenter specific user mangement that changes. administrator@companya.local is different the administrator@companyb.local.

This is of interest to me because I have a horizon pod in one sso domain and on in another that I need to repoint to the other one in the future.Basically I need to do exactly what the post is asking my self