It's not a yellow circle plopped on the image, it's a circle cut out of the photographic paper revealing a yellow surface beneath. He's trying to remind the viewer that this photo, which is supposed to represent a 3D space, is actually a flat 2D surface.
Is it esoteric? Most certainly. Is it "beautiful" or a "great photo"? Not really. But the photographer is bringing to light an interesting point, which somewhere down the road may influence someone else which may eventually influence how we all view photography.
I look at stuff like this as highly experimental, like scientists at a university experimenting with different things without an end goal or commercial application in mind. Some of this stuff is never seen again, but some of it is seen by an engineer who incorporates it into a marketable product.
Take the hardened Gorilla Glass popular in smartphones. It probably started with scientists saying, "We want to see how hard we can make glass, just because we're intellectually curious." So they played and played with stuff and at some point an engineer said, "Hey, we can use this for something."
Or take Hockney's "Joiner" photography. You could take a "better" photo with a good wide angle lens, but I bet that his work inspired research into stitching and eventually Google Street View.