I just realized what has been bugging me about all the Dawnshard's use in the shattering (such as the multi-cut theories).
The issues is one of dimension. Most theories are shown with a circle representing Adonalsium, then divided into 16 pieces like trying to split pizza for a large group. And yes, if there are only 4 "knives" each would have to make 2 cuts.
But, Adonalsium (or Adonalsium's power) isn't a circle, so let's see how a sphere would work:
A sphere (3 physical dimensions) would take a minimum of 3 cuts through the center at right-angles to all previous cuts in oder to get 8 equally sized parts. But going beyond 8 parts to 16 requires 5 cuts (just as annoying as 3 when there are 4 Dawnshards)
However! A hypersphere (4 physical dimensions) would require exactly 4 "cuts" (divisions might be a better word, and its extra weird because those "cuts" are technically a 3-d cell instead of a line) to give 16 equal 4-D objects.
Now, as explained by someone somewhere, I can't remember which book or character, each shard is both bounded and infinite - they have their domain, but infinite power within it.
This is because Adonalsium is/was at least partially infinite. (Going back to the circle division example, if you start from the center you will never reach the crust, the pizza just goes on forever). An infinite thing may still be divided (8 slices of infinite pizza, congratulations, you can now share).
So, if Adonalsium can be represented as a four dimensional hyperplane (the location where all four dimensional objects can be represented - like a square (2-D object) can be represented within a plane), then, with exactly 4 "cuts" you get 16 4-D Orthants/Regions/Shards - each one infinite and bounded.
Continue with the geometry: this would mean that each shard can divide the other shards by how "close" they are:
4 direct neighbors (sharing a 3-D boundary/cell)
6 near neighbors (sharing a plane/side)
4 distant neighbors (sharing only an edge/line)
1 opposite (sharing only the center vertex/point)
It also means that each shard was "cut" evenly by each dawnshard. (Each shard has exactly one boundary by each of the four distinct cuts).
This is all pure geometry and geometric representation, and figures in neither Dawnshard Commands nor Shardic Intent.
Not sure what exactly that means for theorycraft, but it’s something to noodle on.