You're right. To the best of my understanding they were added by someone with a pencil, and certainly not by Matt Jefferies. And it's understandable that even at the scale of the 11 footer they were very subtle and faint.I don't understand etching the gridlines. In the whole "were they they / were they not" debate nobody has ever suggested they were a physical part of the model.
The thing is with a painted on or penciled mark it could be more visible at most angles and under most conditions. But something very finely etched would be visible only when the the light strikes it a certain way and if you're looking at it at just the right angle. And something that fine could easily disappear with a couple of coats of paint sprayed on.
But what this tells me is that they're apparently taking great pains to get this model as right as they can get it. It's an irony that one of these well built could be more detailed and better finished than the original 11 footer even in its heyday. At least this model won't have an uncompleted side.
