It's common knowledge about this particular product. Note the listed 1.78:1 aspect ratio. That was created by cropping the top and bottom of the original image -- widescreen films didn't even exist until the 1950s, so there is no extra image on the sides to add to the standard 1.33:1 version of this 1940s footage.
Note: I believe that just the Blu-Ray version of this is cropped. I don't know about the DVD edition. (I know the original edition was fine; I haven't seen this History Channel-branded version.) Amazon combines all the product reviews for different editions, so complaints about the cropped Blu-Ray get buried under all the positive reviews of the DVD.
No, indeed, since this was originally a made-for-television documentary, all of the footage would have been 4:3, not just the pre-widescreen-era images from the 1940s, because TV sets in the 1970s were all 4:3 fullscreen, not 16:9 widescreen.
But the British owners of the series, Freemantle Media, felt that they needed to deliver a "widescreen" version for HD broadcast, because so many people wrongly associate "HD" with "16:9", so in order to do this, they had to take the original 4:3 (square-like) film image, blow it up and cut off a large portion of the top and bottom of the image in order to make it fit into the rectangular 16:9 frame.
This practice is similar to the way that widescreen films were "panned and scanned" to produce VHS tapes and fullscreen DVDs, but with the shapes of the images reversed (i.e. rectangle to square and not square to rectangle).
The company apparently could not afford to make a separate HD master for their Blu-ray edition in the UK, and A&E can only release what they receive from Freemantle to the USA, so the US release is also cropped in the same way.
The audio is so bad on the DVD set that I will absolutely trade a somewhat cropped image in exchange for a remastered soundtrack. Olivier won an Emmy for his narration of this series and he's often barely audible on the DVD version.
To Aaron Silverman; I agree. Here is my reply post to the latest 5 star review of this unfortunate tragedy:
You are correct in saying that this is indeed one of the greatest documentaries ever made. However, you are incorrect in saying that "not a single detail was missed", because tragically the producers of this blu ray release cropped off 25% of the visible frame (top and bottom) and threw it in the trash. Because this blu ray is now considered to be the "definitive" version of this amazing and important documentary, unfortunately it is most likely what future generations will be left with. In my opinion, when Fremantle Media was given the rights to this historical documentary, they were given a grave responsibility, and what they ended up doing is committing the crime of vandalism against an important historical work of art. You recommend that WW2 aficionados "go out and GET IT!!" I recommend that this type of egregious negligence and recklessness be boycotted.