I guess it just means that they are certain it will work with their phone kit. I'm having a bluetooth put into my new civic next month and before they would confirm the order, they went to check if my phones were compatible with the kit, or else they wouldn't have sold it to me.
I have a Blackberry Curve and a Nokia N96 paired to my HFT. The Blackberry is fully compatible and works a treat, the N96 is not officially compatible but is capable of phonebook transfer etc.
That said, the Nokia has a habit of connecting to the system when it wants to be conected to it, and has a habit of rebooting itself and then not being visable to the HFT.
I conclude from this that some phones that are "not compatible" with the HFT simply because they are unstable, and Honda quite rightly does not want to put it's good name against some of the shoddy and rushed to the market phones that Nokia and perhaps others are putting out there.
Also worth noting that "compatible" does not always mean full functionality. A compatible phone may not have the ability to transfer its phonebook. However, as long as you can find a phone that will transfer its contacts, then any paired phone can access it.