While on my Thurs PM run I stopped to take a close look at fences along my route.

It appears that the Fence Buddy assumes that the fence has been assembled using a pre-bent clip which has open ears and that the ears remain open after the fencer has moved on.

On the fence I looked at, the "clip" was made of fence wire wound around the barbed strand on both sides and had up to 4 turns on both sides. No way the Fence Buddy would work on those fences.

I also found a fence made of 8 horizontal strands on non-barbed wire. No spreading that one or going under. Didn't look closely to see what would happen if one were to put weight on any given wire.
At least it wouldn't bite while trying it out.