How to check if the plane detected in WebXR's hit test results is vertical?

Question

I am new to WebXR and trying to only allow the reticle to show up if the plane detected is vertical (like a wall). I am following this basic hit test example as a starting point. I don't see any parameter for vertical detection of the plane but in the demo, the reticle changes color when it's on a vertical wall.

Am I missing something here? Is there a way to only show the reticle if the plane is vertical?

I can see the position and rotation of the reticle being set here:

let pose = hitTestResults[0].getPose(xrRefSpace);
        reticle.visible = true;
        reticle.matrix = pose.transform.matrix;

Is there a way to access reticle orientation from this?

Demo: https://immersive-web.github.io/webxr-samples/hit-test.html