I am saying that
if you think eternalism precludes change or motion, you are misunderstanding eternalism, because I am an eternalist, I've read the views of other eternalists plenty, and none of us deny that change or motion happen. The only claim is that change in n dimensions over an extra dimension is equivalent to a static figure in n+1 dimensions.
How can you give the diameter of a mountain without specifying at which altitude you mean? The mountain has different diameters at different altitudes.
How can you specify the height of a person without specifying at what age you mean? Or perhaps even more illustratively: how can you specify the position of the hands of a clock, without specifying at what time you mean?
In both the case of the mountain and the case of my height or the position of the clock hands, we assume we mean the indexical value of the dimension across which it varies: the one that we're at. When we ask the diameter of a mountain, by default we mean at the altitude that we're at, unless there's some context where it's been established that we're talking about another altitude. When we ask the height of a person, we mean at their current age; when we ask the positions of the hands of a clock, we mean at the present time. Unless there's some context where it's been established that we're talking about another time. But in any case, if something about a given thing changes across some dimension that is spans -- a dimension of space, or a dimension of time -- you have to specify at which point in that dimension you want the measure to be taken.
Let me try another analogy. There is a highway that runs from the nearest big city to my little mountain town. It runs north-south, going uphill in the northward direction. It has four lanes each direction as it leaves the big city, and only one lane in my little town. There's a sign where the lanes decrease that warns that the road narrows, like this:
You (and MU) seem to think that that sign is lying. "The road doesn't actually get narrower. The road is the same width it's always been, unless a construction crew has just been through to remove some lanes. The road is the same width always, unless it changes over time. There is no sense in which the road 'gets' narrower as it 'goes' north up into the mountains. The road has fewer lanes in the north up in the mountain town than it does down south by the coastal city, but it's not 'changing' its width with latitude or altitude!"
That sounds like willfully misinterpreted nonsense thinking to me, trying to prove a philosophical point against a view that nobody actually holds.