I believe I am experiencing this with the VP180, but it is very slight and not likely to be noticable under normal listening conditions. Most of my friends only noticed it once I pointed it out to them and they started testing and listening for it, while two of them didn't notice it at all, even after I tried to explain it to them.
If it’s very slight then do yourself a favour and stop listening for it right now or you will end up quite insane like me.
Personally, I found it more noticable with vocals (ie. singing) and less noticable with dialogue during movies. This may have more to do with the fact that movie dialgue bounces from actor to actor with sound and/or effects in the background, so it's masked somewhat.
I also notice it more with music. I agree with your reasoning and would add from what I’ve read that in many cased the sound engineer will mix some of the center channel into the mains to get a more seamless soundstage for movies especially with things moving and panning around the screen.
Thanks for the detailed explanation. If you were hearing the “hollowness” in my experience it’s never subtle so sounds like its not there.