See the comparisons below:
The backyard photos aren’t great quality so one can’t be 100% certain but it doesn’t look identical to the Book Depository rifle in my opinion. You can clearly see the front strap is on the bottom in the BYP, not on the side of the barrel…
I like the way you start off saying the "backyard photos aren’t great quality so one can’t be 100% certain", before then pronouncing you "can clearly see".
Just to clarify - you
can't clearly see where the strap is connected to the rifle. The quality of the photo is too poor to discern that. In my view, the way to determine where the strap is connected to the barrel of the rifle is to follow how the strap is hanging from the rifle. Gravity will pull the strap down from the point it is connected to the rifle (IMO).
In the pic below I have highlighted (with a red arrow) where the strap appears to be connected to the rifle.
"As we can clearly see", the strap is connected to the bottom of the barrel of the rifle and not the side. I believe there is a bit of excess strap material that bends off to the right after the connection and it is this you are using for your determination as to where the strap is connected to the rifle.