Hello, Mark!
First off, thank you for writing the Commonsware books — I used them a decade ago when first learning about Android, and am using them now for my job, and REALLY appreciate how detailed and clear the Kotlin book is. :)

main activity (CoordinatorLayout) [1]
  includes bottomsheet layout (LinearLayout with BottomSheetBehavior) [2]
    has a NestedScrollView (or FrameLayout, in other tests) [3]
       into which a fragment is inflated [4]

both [2] and [3] have been getting extra padding, but [1] and [4] have not

        fun setExpandedTouchArea(view: View, extra: Float) {
            val parent = view.parent as View
            val extraSpace = extra.roundToInt()

            parent.doOnLayout {
                val touchArea = Rect()

                view.getHitRect(touchArea)

                touchArea.top -= extraSpace
                touchArea.bottom += extraSpace
                touchArea.left -= extraSpace
                touchArea.right += extraSpace

                parent.touchDelegate = TouchDelegate(touchArea, view)
...