Lego Exoforce Mobile Defense Tank variety?

[BlazeBind]

So.. I started trying to assemble some of my older lego sets from my giant box of mixed pieces from various sets i got throughout the years. I knew i had the pieces to the Mobile Defense Tank from Lego Exo-Force. So i looked up the instructions booklet on the interwebs and came across something pretty confusing. 

First look at the front box image.
 

Spoiler

 

Now look at the finished version in the instruction booklet from LEGO's official site.

Spoiler

Notice something? Yes. The Bar between the tracks is missing from the actual build. 

Spoiler

The bar can be slightly be seen on the rear tracks also, on the box image, but they are not in the actual build. 

There's more... Things got even more weird, because it turned out that i have been following two different instruction booklets...

 On this website: http://lego.brickinstructions.com/lego_instructions/set/7706/Mobile_Defense_Tank

I found the instructions in the image below. These instructions show, that the bar between the tracks is put into place. But on the instructions you can download as PDF on top of the page, the bar is not included. The bar is not included in the instructions on LEGO's official site either.

Spoiler

Looking through both instructions, there are actually a few more things that is different. The build of the canopy varies also.

Spoiler

Even the parts list in different.

Spoiler

Now... Can anyone explain what is happening? I have been browsing the interwebs for hours, trying to figure out if there is more than one version of this build but i cannot find any evidence. Did they change the build over time or what is happening? I really hope someone can explain this to me.

 

 

Edited December 13, 2016 by BlazeBind

[samurai-turtle]

Well for the "jungle" series.  Two of my sets have a extra page for the instructions. So, they obviously change some thing after the instruction books were made. But, if you look to more recent sets (like WALL-E & Ant-Man) stuff had to be changed on them for quality reasons. If I had to guess for your example, I might just say it was human error. Someone did not proofread the instruction book to the maximum efficiency. 

[zux]

It has happened previously that LEGO reviewed the model while it was already in production and released slightly modified model. I had same case with 8858 model. My instructions were for an initial version while everything that was available on the internet is a later slightly changed version.