BezierTo breaks when aligned on the YZ plane

BezierTo produces a straight line, rather than the expected curve, when everything is aligned in the YZ plane.

I've attached an example below. The first polyline is the wrong one. The other two -- one with a slight adjustment and one in the XZ plane -- are behaving properly. Any deviation from alignment appears to make it work correctly.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Shapes;

public class ShapeTest : ImmediateModeShapeDrawer
{
    public override void DrawShapes(Camera cam)
    {
        using (Draw.Command(cam))
        {
            Draw.LineGeometry = LineGeometry.Flat2D;
            Draw.ThicknessSpace = ThicknessSpace.Pixels;
            Draw.Thickness = 4;

            using (var p = new PolylinePath()) {
                p.AddPoint(Vector3.zero);
                p.BezierTo(5 * Vector3.up, 5 * Vector3.up + Vector3.forward, Vector3.forward);
                Draw.Polyline(p);
            }
            using (var p = new PolylinePath()) {
                p.AddPoint(Vector3.zero);
                p.BezierTo(5 * Vector3.up, 5 * Vector3.up + Vector3.forward + Vector3.right * 0.001f, Vector3.forward);
                Draw.Polyline(p);
            }
            using (var p = new PolylinePath()) {
                p.AddPoint(Vector3.zero);
                p.BezierTo(5 * Vector3.up, 5 * Vector3.up + Vector3.right, Vector3.right);
                Draw.Polyline(p);
            }
        }
    }
}