If I recall correctly the original flaming skull was supposed to glow in the dark. When he showed sneak peaks it did not come with many positive reviews so he sculpted a totally different flaming skull (the one that is now included) this one however does not glow. I believe everyone thought the original looked too much like ghost rider. I think this one is darker causing the glow option to go out the window. In my opinion the new skull looks much better and from someone that has had statues that glow, you really don't use that feature that much. At least this guy didn't.
Say what you will about PCS, but it is nice when a company knows the general public does not like a certain part of a statue that they took the time (and cost) to make it better.
You can check with someone that is more in the "know", but I'm pretty sure that is what happened to the glow feature.