Animation via AnimatorController created in script does not play in Unity

I have created an empty GameObject and assigned it a script: Main.cs.

public class Main
{
    [MenuItem("Custom workflow/Initialize")]
    static void Initialize()
    {
        // Place a text mesh on the scene
        var obj = new GameObject("Sample");
        obj.transform.position = new Vector3(0, 0, 0);
        var text = obj.AddComponent<TextMesh>();
        text.text = "Hello world";

        AnimationClip clip1 = CreateAnimationClip();
        AnimatorController sm = CreateSimpleAnimatorController(clip1);

        var animator = obj.AddComponent<Animator>();
        animator.runtimeAnimatorController = sm;
        animator.applyRootMotion = true;
    }

    private static AnimationClip CreateAnimationClip()
    {
        var translateX = AnimationCurve.Linear(0.0f, 0.0f, 2.0f, 25.0f);
        var animationClip = new AnimationClip();
        animationClip.SetCurve("", typeof(Transform), "position.x", translateX);

        AssetDatabase.CreateAsset(animationClip, "Assets/procanim.anim");

        return animationClip;
    }

    private static AnimatorController CreateSimpleAnimatorController(
      Motion motion1 = null, Motion motion2 = null)
    {
        // Creates the controller
        var controller = AnimatorController.CreateAnimatorControllerAtPath(
          "Assets/SimpleStateMachineTransitions.controller");

        // Add parameters
        controller.AddParameter("GoToB", AnimatorControllerParameterType.Bool);
        controller.AddParameter("GoToA", AnimatorControllerParameterType.Bool);

        // Add StateMachines
        var rootStateMachine = controller.layers[0].stateMachine;

        // Add States
        var stateA1 = rootStateMachine.AddState("stateA1");
        stateA1.motion = motion1;
        var stateB1 = rootStateMachine.AddState("stateB1");
        stateB1.motion = motion2;

        // Add Transitions
        var transitionAB = stateA1.AddTransition(stateB1);
        transitionAB.AddCondition(AnimatorConditionMode.If, 0, "GoToB");
        transitionAB.duration = 0;

        var transitionBA = stateB1.AddTransition(stateA1);
        transitionBA.AddCondition(AnimatorConditionMode.If, 0, "GoToA");
        transitionBA.duration = 0;

        return controller;
    }
}

The problem

As I invoke the menu item, I get all assets in place. When I hit play, nothing happens. I can see state stateA1 is on, but the animation does not run. If I click on the text object in the scene...

...this is what I see in the animation window:

I think the problem might be here:

animationClip.SetCurve("", typeof(Transform), "position.x", translateX);

Because, when I remove the code generate Transform.position property from the animation timeline and manually add one via UI, it works once I hit play again.