It's only "Clear" that you are OB on the other side, if you are either close to the line, or far away from the ends of the line. But the problem is, OB doesn't just end. How does it just end? The line ends, but the OB continues in one direction or the other. And if it isn't made clear in one way or the other, how do you decide which direction. The only logical and practical thing to assume is that it continues. We don't have any way to properly measure and estimate a 90 degree angel, especially if the disc is relatively far away from the line.
I'm pretty sure the green "dot" is supposed to be the basket, and the orange rectangle might be a teepad, but that may be wrong. In either case, it doesn't change the fact that the rules defines OB as an area, not a line, nor does it mention anything about the TD's intentions, or how to assume a line continues when it stops. It's poorly defined OB, and it doesn't matter how much we discuss it, there really isn't any definitive answer.
If the OB was defined as being left of the line, I would say the area is defined.
And estimating the direction of a 90 degrees angle should not be significantly harder than estimating the continuation of the line.
But definitely a badly defined OB. That scenario should have been anticipated by the TD.