* It is the functional essence of a hierarchy that properties of parental objects are inherited by the children nodes.
1 You can use a group, consisting of base plate and hinged attachment on the same level (ie no hierarchy) and this will work.
2 You can apply a burn transform (as per Frank) to reset the parameters to the original values.
3 Preferable, ignore the scale parameters (again, as per Frank) and use the Width/Height/Length parameters. Of course, this only works with cuboid primitives. For others (sphere / torus / ...) you can deploy a transform modifier. Toggle this off in the object browser if you need to tweak the primary settings. No need for an object to be editable, you can stick with parametric primitives out of the box.
* There is an indication of the shear-status by the transform widget being distorted as you can see in your screen shot. You get instant feed back from the GUI that the axes of the current sub-object (the hinged plate) are not orthogonal / perpendicular but sheared. Rotation on a pivot generates acute / obtuse angles in most degrees of rotation.
* If you know what you are doing, you can use this shearing for rather weird animated distortions. This is quite useful in biology for cheap tricks.
* Note that any such distortion is also passed on to any modifiers in the hierarchy.