The problem is: it is outside of the right MLG tire marks!
That definitely caught my eye too! More to the point is that it seems so perfectly parallel to the main wheel skid mark for so far. The plane was severely yawed, and something was keeping it yawed at exactly that angle. It was halfway between a ground loop, and returning to being aligned with the path of motion, very unusual, I can't imagine being able to make a plane do that, though asymmetric power could be an element. I don't know if a B17 tailwheel locks or not. If it were locked, and making a skid mark like that, the tailwheel would have been really trying to align the plane. If the tailwheel was free castoring, it may just have been along for the ride, while a combination of ground loop forces, application (or not) or rudder, and perhaps asymmetric power were factors.
There have been times while training a tailwheel pilot, that I've had to remind them to pull the power off after touchdown....