I think the 9 prefix always designates a reference board design in the Broadcom part numbering scheme. I'm not 100% on that though as I've never seen a definitive part numbering guide from them.
Also worth noting that the BCM6368 chipset has a GigE switch embedded but the reference board design (BCM96368MVNGR) only implements fast ethernet (100Mbps) physical connections.
The reasoning behind that seems to be an EU guideline on power consumption which suggests (haven't done the maths) that you can't have GigE and FXS ports on the board and stay within the power consumption guidelines. Use of FXS ports is virtually unheard of with any UK ISP but they do get used in other EU countries (Teliasonera springs to mind).
Probably shaves a couple of pennies off the hardware cost too. Oh and it will no doubt reduce support costs to ISPs - I wouldn't want to be the one explaining to a clueless end-user why they can't get 1Gbps on the LAN