Windows Vista and Windows 7 Clients do not register the PTR record by default when DDNS updates are done. In Windows environments the DHCP Server is responsible for performing PTR record registration on behalf of the client.
With UCS / Samba4 the DHCP Server can't do DNS updates by itself so the updates are directly triggered by the clients.
The clients can also tigger the PTR registration themselves if Use this connection’s DNS suffix in DNS registration is selected in adapter properties. The GPO which does the exact same thing is located in Computer Configuration -> Administrative Templates -> Network -> DNS Client and is called Register DNS records with connection-specific DNS suffix.
The DNS Client Service, responsible for DDNS updates since Windows Vista, will then create the PTR record in the first matching reverse zone which is found (starting at the “biggest”).