The "Not" Keyword

Instead of hijacking the other topic any further, I decided to create a new topic for the discussion of the "Not" operator. 

Here is the previous topic for reference:

http://www.autoitscript.com/forum/topic/152795-reset-value-if-value-is-static/

How is it that this works perfectly (tested and part of one of my toolsets that hundreds of techs use daily):

$Authentication = InetGetSize("http://wouldntyouliketoknow.com/DeleteThisNow.txt")
 
If Not $Authentication = 0 Then
    MsgBox(16, "ERROR", "The license for this product has expired.", 5)
    Self_Destruct()
    Exit
EndIf

As we can see, there are no parenthesis there, but it still functions as I expected. This also works as expected, but I feel that the 2 contradict each other:

#include <Constants.au3>

Local $vVar = 'SomeTest'
; This expression before Then is Not True, as $vVar = 'SomeTest' evaluates to True, hence Not True.
If Not ($vVar = 'SomeTest1') Then MsgBox($MB_SYSTEMMODAL, '1', 'This MsgBox won''t display, as $vVar = SomeTest.')
; AutoIt looks at this as (Not $vVar) = 'SomeTest'.
If Not $vVar = 'SomeTest1' Then MsgBox($MB_SYSTEMMODAL, '2', 'This MsgBox won''t display, as $vVar = SomeTest.')

In this second example, the MsgBox with title '2' does not launch, proving that parenthesis are a necessary part of the statement. My question is: What it is about my first example script that makes it work differently than the second example by FireFox?