At least not for me, my Windows box didn't get an IP if I enabled the Prefix for the internal interface, I had to leave that at off and manually do a DHCPv6 server.
As explained in the IPv6 tutorial, it also depends on the Client OS if you additionally need DHCPv6 for Auto-Configuring DNS as well. For Windows, you need both Prefix Advertisements for IP-Assignment as well as DHCPv6 for DNS-Settings.
