I think this is actually running into something fundamental that tends to render the endeavour either too trivial, or too hard. Remember the old 2D version, and clicking somewhere in the middle, and then having a circlish region in the middle of the board open up. You could always very easily identify mines that were denting the ring. I mean, if the ring had regions of convexity instead of all being concave, it was easy to push out and expand the known region till it was concave.
Here, to get lots of regions that are concave like that you'd need the mines to be distributed as along some set of bubbles that are filling the region. Just uniformly randomly scattering isn't going to get the right sort of boards, whereas it does in the 2d case.
What I'm saying is, after the board opens up a bit, using sweep, its very easy to identify mines that are on the boundary of unknown cubes, with just a single 1 next to them, and then you just keep pushing the known region open. So, there's a slower opening up, but after things are going in your way, it flows very quickly to the end, whereas in old minesweeper, it never really got into that trivial phase except right at the end. But here, it seems to have a very long phase of ease.
If you made a whole lot of extra mines, you might avoid that, but then it would be too tricky.
But it is very well done, and quite interesting.