mipmapCount for Cubemap and Texture3D

Texture2D has the mipmapCount field, but Cubemap and Texture3D (and possibly other Texture-based types) don’t. You can use GetPixels/SetPixels to access data for a particular mip level, but as far as I can see you have no way of determining how many there are.

Is this just an omission, or are there other ways of finding out the same information?

I am under the impression that calling Texture3D.SetPixels32() with a particular miplevel is being completely ignored. That is on Windows/Nvidia/Unity 5.4.0f3.