Why when using ThrottleLast can't change text correctly?

[heroliss]

using UnityEngine;
using UnityEngine.UIElements;
using R3;
using TMPro;
using System;

public class UITest : MonoBehaviour
{
    [SerializeField] UIDocument uiDocument;
    VisualElement uiRoot;

    [SerializeField] TextMeshProUGUI label;

    ReactiveProperty<int> clickCount = new(0);

    private void Start()
    {
        uiRoot = uiDocument.rootVisualElement;
        var buttons = uiRoot.Query<Button>().ToList();
        foreach (var button in buttons)
        {
            var clickStream = Observable.FromEvent((action) => button.clicked += action, (action) => button.clicked -= action, destroyCancellationToken);
            clickStream.Subscribe(_ =>
            {
                clickCount.Value++;
            });
        }

        // Issue occurs here:

        clickCount.ThrottleLast(TimeSpan.FromSeconds(1))  //---> When using ThrottleFirst, text changes are displayed correctly
            //.ObserveOnCurrentSynchronizationContext() //---> When this method is added, text changes are displayed correctly
            .Subscribe(x => {
            label.text = $"Click Count: {x}"; //===> When using ThrottleLast,  label.text changes are visible in the inspector, but not updated in the Game View. Why?
        });

        label.text = "111"; // this is correctly
    }
}

unity 6000.2.10f1

[GallopingDino]

The difference is that ThrottleFirst calls observer.OnNext synchronously, and ThrottleLast uses an internal timer to invoke observer.OnNext. By default this timer is not synchronized with Unity's main thread, therefore the method in Subscribe can't properly interact with Unity API. To fix this you need to integrate Unity support for R3. Have you done this?