Excuse me Mr Newwell, but wasn't Halflife 2 using the havok physics engine? should the coders have nothing to do with it?
Puting HL aside for the moment and just addressing that statement on its own...
I know it was meant (somewhat) in jest, but for the record a giant piece of 3rd party software like a physics engine doesn't just attach itself to your own code like a magic Lego. Nice as it would be, the truth is it can be a real time consuming pain in the ass to make the two meet in a useful way. Sound engines, video players -- those are easy. But physics is a lot more pervasive since it needs to get involved in so many aspects of your engine in order to do its thing. So yeah, the programmers have a lot to do with it.
Getting back to HL... Valve should really just shut up until it's done. No one's going to "forget" about HL2 if there isn't any press on it for a couple/few weeks. So either they're not as close as they say they are or they just don't know when to put a cork in it.