Exactly, that's how it works in Vintage Story
Not exactly though since the blocks can be highly varied sizes and rotations - the voxels use floating point dimensions and angles. People are posting small very detailed blueprints all the time that you can use as decorative clutter - and they are all made with blocks.
You could in theory do it subtractive and drag out a volume of 0.01x0.01x0.01 blocks and pickaxe it down block by block.
Or do it additive like a 3D printer does and print it layer by layer (in fact a 3D printers .STL file importer would probably be a good plugin!)
Or you could start with 1x1x1 blocks rough out the core shape, then start removing and adding sections of 0.1x0.1x0.1 blocks, then further step down to 0.01x0.01x.0.01 blocks.
Or get some Lego plans and make all the various block sizes it uses in different colors.
While the pickaxe looks like a very rough tool to be whittling with, that is just a cosmetic - the actual block it is removing is whatever the cursor is on - and you can change the cursor to be just a dot if you want.
Now why would you want to only use a square block and none of the other block shapes? I guess creativity is borne from constraints.
You would only want to do this for the occasional art project statue because too many blocks in a chunk will get laggy.