Hi there Tom,
Thank you so much for posting this question.
Regarding your first concern:
As far as i know, there is huge quantity of changes from both versions. On UCMDB 10, we can define if an IP is a Datacenter (Server) or if it is a Client (Work Station or Laptop). As you may know, most of Enterprise Environments has Static IPs for service servers and DHCP for work stations. UCMDB takes advantage of this to set the IP as a high or low priority thing to take in count at any identification/reconciliation time. So, as a recommendation, ensure your customer have set correctly this option on the IP ranges on the probes (Server IPs as Datacenters and Workstation IPs as Clients). This way, if the IP changes the UCMDB will know if this change need to be taked in count or no.
Please, check the History of the Relationships. You will see why and who created this relationship. Maybe you can catch the idea why the relationship was created. If your customer still thinks this should not happen, i reccomend you to open a support case.
I hope this information helps.