WebView2: Setting object properties in C# from Javascript code

Here's a followup to this question.

I'm porting a WPF app from CEFSharp to WebView2. I have a HostObject that needs to be accessible from js in the WebView2 window. This is it, stripped down.

using System;
using System.Runtime.InteropServices;

namespace webview2Demo
{
    [ClassInterface(ClassInterfaceType.AutoDual)]
    [ComVisible(true)]
    public class Api
    {
        public string Username { get; set; }
        public string Version = "1.1.1";
        public Api()  //ctor
        {
        }
    }
}

I can use this line successfully in the WebView2 control's NavigationStarting event to make the object visible from Javascript. So far so good.

webView.CoreWebView2.AddHostObjectToScript("api", new API());

I can retrieve public properties and members like this. So far so good.

(async function foo () {
  const api = chrome.webview.hostObjects.api
  const ver = await api.Version
  alert (ver)
})();

My problem: Can I reliably, without any sort of asynchronous race-condition or deadlock risk, set properties like this? api.Username = 'whoever' It seems to work but I haven't found it documented.

(async function foo () {
  const api = chrome.webview.hostObjects.api
  api.Username = 'whoever'
  const user = await api.Username
  alert (user)
})();

The documentation says the HostObject is exposed through Promises. Am I hitting the setter correctly?

from WebView2: Setting object properties in C# from Javascript code