He called him Philip because he was talking about him in real life, not as the character CM Punk. And they did have heat with each other (Punk said Rock doesn't deserve the credit he gets for the WM27 buyrate when he did nothing meaningful there and he called him an asshole backstage at Survivor Series later in the year) but they've made up for it since then. Just like Rock and Cena, who I saw hugging in a video backstage after their WM28 match.
Anyway, I still don't see the problem with Rock winning the belt. As mentioned, it'll perhaps bring a lot of attention to the product and probably make headlines that 'movie star The Rock/Dwayne Johnson won the WWE Title again" and as a fan, it'll be cool to see him with the belt again. Also, he's gonna be involved in the main storyline heading into WM29 as it is, and if that program is for the belt, then what difference does it make whether he's champ or not? Lastly, who else could beat Punk for the belt? He's beaten pretty much everyone else at this point (Cena, Bryan, Jericho, Del Rio, Kane, The Miz, etc.) Ryback would have been a good choice, but he's already failed to win the belt twice now, and a third time coming up in January. Undertaker would be terrible considering he can't even work a full schedule anymore. Sheamus is the only other choice, but do you really want to see that? (And to be absolutely technical, Punk beat him once already on Main Event as well.) Rock is almost the only fresh opponent that is left.
All this being said, I still have a lingering feeling Punk will retain at the Rumble, but won't care at all if he doesn't.