I also worked in digital signage a few years back. We had a similar kind of refrigerator in our office, likely with an LG screen. The door/screen was transparent glass like the old fashioned ones and a layer of LCD. The upside of that kind of design is that the see-through door still works if the screen is off. And of course, you actually would see the real contents of the refrigerator once it's digital signage content deactivated (e.g. detected people by camera). On top of that, depending on the animation you would see through darker parts of the door to get a peek of the actual products inside (useful if you're unsure what you're looking at).

IIRC we displayed our office calendar on it, among other things.

On the other hand, the screens in the article seems to have made away completely with the glass, leading to completely opaque, black rectangles if they are not running. What a mess.

probably more readable though. With the displays at the time you could see through even the blacks it was like 50% transparent when displaying a totally black screen. Means you could see through it but the images you put on the display needed to be fairly simple and .. id dunno 'blocky' because depending on what was behind the glass it could get very visually confused.