If you look closely, you'll see in the 2nd picture on the left size, it says "8-10 in", meaning it has the wrench ends of an 8" wrench and a 10" wrench. This means that one side is slightly larger than the other.
Here's an eBay listing that has slightly better pictures of what I think is the same model of wrench.
To me, the slight difference in the head size without the added length of a 10" wrench doesn't make the tool that much more useful than if they simply had the 10" head with a shorter handle.
However, a dual headed adjustable wrench seems to be somewhat common(?) for older tool sets, as I found a variety of different versions.
And a forum talking about different varieties, as well as what they are and why they were made/used.
I'm just guessing here, but this may have made more sense when steel and/or tools were relatively more expensive than they are today. There's also a semi-common modern desire to "own all the things/tools", while older generations bought only what they needed, and only if something couldn't be repurposed or wrangled into working.
Also, some work pants used to have a long, thin pocket or denim loop that could basically store exactly one wrench down the side of the leg (before cargo pants/shorts). Overalls and coveralls also tend to have these pockets and loops. If you had to choose what wrench you wanted to put in the pocket or loop, the double headed wrench might fit the need. Growing up on the farm, we often kept a hammer in the loop, but not everything is a nail.
I found a modern version that has both the loop and the pocket (2 pockets in this case).