You WOULD ask that (I didn't save the pages I was working from). I did a huge search for Enterprise images to compare to, and was surprised to note differences just about everywhere. (And it didn't help that I used a few different published 'schematics' as reference as well, which were all different).
Anyway, what I saw was that this odd marking was present on all the shots I found (and slightly different on each), but that the small struture that protrudes forward was on SOME shots, but not all. I split the difference, though...
Again, though, if the consensus is that the little structure be put on, I'll happily do it.
EDIT: THERE We go -
TWOK Screenshots shows the marking (slightly different), but not the protruding housing in front of the impulse deck.
Also, the self-destructing Enterprise in TFSF has the same markings and structure. The TUC Enterprise also has the same set up. I'm
guessing it was a change made between TMP (which has the structure and different markings) and the other movies.