I've added a torus and and then a cylinder to the middle of it and tried to delete the cylinder from the torus, but instead of deleting the vertices within the cylinder object, it just makes a cut through the torus.
I've tried recalculating the normals of both objects to be outside and then inside (same for each). I've deleted loose vertices (there shouldn't have been any, but the torus had a few).
I tried triangulating the large faces on the top and bottom of the cylinder.
I've made sure the cylinder overlaps the torus in the z direction by a lot.
I haven't modified either object in any way other than through their numeric parameters (scale, dimensions, etc).
I've applied all transforms.
Any insight as to why these two basic meshes created by Blender itself won't boolean difference?