Strange behavior of undocumented RawArray and ArrayObject expressions

Question

I discovered several strange results and inconsistencies while trying to understand what undocumented RawArray and ArrayObject really are:

image = ImageResize[Import["http://wolfram.com/favicon.ico"][[1]], 1];

rawArray = ToBoxes[image][[1, 1, 1]]
(* RawArray[Byte, <1,1,4>] *)

rawArray // Head
(* RawArray *)

rawArray // Length
(* 2 *)

rawArray // InputForm
(* RawArray["Byte", {{{237, 153, 142, 255}}}] *)

Hold[RawArray]["Byte", {{{237, 153, 142, 255}}}] // Depth
(* 5 *)

rawArray // Depth
(* 2 *)

rawArray[[0]]
(* Part::partd: Part specification RawArray[Byte,<1,1,4>][[0]] is longer than depth of object. >> *)
(* RawArray *)

rawArray[[1]]
(* Part::partd: Part specification RawArray[Byte,<1,1,4>][[1]] is longer than depth of object. >> *)
(* "Byte" *)

arrayObject = rawArray[[2]]
(* Part::partd: Part specification RawArray[Byte,<1,1,4>][[2]] is longer than depth of object. >> *)
(* ArrayObject[Byte, <4>] *)

arrayObject // Head
(* Language`ArrayObject *)

arrayObject // AtomQ
(* True *)

wdx = ExportString[arrayObject, "WDX"];

ImportString[wdx, "WDX"]
(* {{{237, 153, 142, 255}}} *)

% // Head
(* List *)

Uncompress[Compress[arrayObject]]
(* {{{237, 153, 142, 255}}} *)

arrayObject // FullForm
(* List[List[List[237, 153, 142, 255]]] *)

arrayObject // InputForm
(* Raw[Language`ArrayObject, "78c4801b00000000"] *)

inputFormStr = ToString[arrayObject, InputForm]
(* "Raw[Language`ArrayObject, \"78c4801b00000000\"]" *)

heldArrayObject = ToExpression[inputFormStr, InputForm, Hold]
(* Hold[Raw[Language`ArrayObject, "78c4801b00000000"]] *)

heldArrayObject[[1, 0]]
(* Raw *)

heldArrayObject[[1, 1]]
(* Language`ArrayObject *)

heldArrayObject[[1, 2]]
(* "78c4801b00000000" *)

arrayObject2 = ReleaseHold[heldArrayObject]
(* 0 *)

arrayObject2 == 0
(* 0 == 0 *)

% // FullForm
(* Equal[1, 0] *)

ToBoxes[arrayObject2]
(* 0 *)

% // Head
(* Integer *)

arrayObject2 // Head
(* Language`ArrayObject *)

arrayObject2 // AtomQ
(* True *)

wdx = ExportString[arrayObject2, "WDX"];

reimported = ImportString[wdx, "WDX"]

(* Raw::string: String expected at position 2 in Raw[Language`ArrayObject,78 c4801b00000000]. >> *)
(* Raw[Language`ArrayObject, 78 c4801b00000000] *)

reimported // FullForm
(* Raw[Language`ArrayObject, Times[78, c4801b00000000]] *)

reimported // AtomQ
(* False *)

reimported // Depth
(* 3 *)

Uncompress[Compress[arrayObject2]]
(* "<---RAW DATA--->" *)

% // Head
(* String *)

Note that Part reports errors when invoked on a RawArray, but still is able to extract parts. ArrayObject has completely different representation in InputForm and FullForm, and turns into a List when reimported.

Is this behavior normal? Or there are some bugs? Is it because these parts were not supposed to ever be seen by humans?

Are there situations when one needs to explicitly construct or manipulate by RawArray or ArrayObject expressions? What is their real meaning?