With shapes that reference categorical axis, shape is drawn when no category exists

For the following rendered graph, the shape is described like this:

 {
        "line": {
          "color": "yellow",
          "width": 3
        },
        "type": "rect",
        "x0": "A",
        "x1": "A",
        "xref": "x",
        "y0": 0,
        "y1": 0.5,
        "yref": "paper"
      }

There is no category "A" on the x axis, but the shape is still drawn and appears to be drawn at the centre point of the x axis.

Here is a codepen:

https://codepen.io/liamconnors/pen/XWLmRae

Start by running the linked CodePen and reproducing the shape configuration against a categorical x axis with no "A" category. Trace the shape-rendering path for categorical axis references; done means the rectangle is not drawn when its referenced category does not exist, while valid category references still render.