Here's me demonstrating the same thing happening in Maya https://www.dropbox.com/s/niv2geptee4jfso/2017-08-24_21-35-28.mp4?dl=0 Forgive me trying to dock the UV toolkit panel, seems to be a bug. Transformations -> Components are a hierarchical thing that exist in most 3D software.
Haven't used blender but lookup a way to freeze the mesh before you unwrap. This is happening because of two different types of "Spaces" that things are taking place in. The object space is still the same as the original cube which you were given, which is why it's unwrapping like that. You are applying a scale at an…