Why function at AddScriptToExecuteOnDocumentCreatedAsync is called only after source change ?

I have a simple application with WebView2.
In my InitializeAsync method, I add 2 scripts via AddScriptToExecuteOnDocumentCreatedAsync.

async void InitializeAsync()
		{
			await webView.EnsureCoreWebView2Async();
			webView.CoreWebView2.WebMessageReceived += RecievedMessage;
			webView.CoreWebView2.DOMContentLoaded += delegate
			{
				IsDOMLoaded = true;
			};

			await webView.CoreWebView2.AddScriptToExecuteOnDocumentCreatedAsync("document.addEventListener('mouseup', function(event) { var res = window.getSelection().toString(); var myObj = {action: 'Selection', data: res}; var json = JSON.stringify(myObj); if(res.length > 1) { window.chrome.webview.postMessage(json); } }, false);");

			await webView.CoreWebView2.AddScriptToExecuteOnDocumentCreatedAsync(
				"function getTextHTML(){var res = document.body.innerText; var myObj = {action: 'GetHTML', data:res}; var json = JSON.stringify(myObj);window.chrome.webview.postMessage(json);}");
		}

Then after button click which should Execute the second script - nothing happens.

private async void ButtonClick(object sender, RoutedEventArgs e)
		{
			await webView.CoreWebView2.ExecuteScriptAsync("getTextHTML();");
        }

But first await webView.CoreWebView2.AddScriptToExecuteOnDocumentCreatedAsync("document.addEventListener.... works fine at start page.
In order to call my second function, I need to reload a page or go to another page.

My question is:

Why it has such behavior and how can I fix it?

Besides, I'd like to know, how I can ensure that script was added? Once, I found my script somewhere after clicking F12 on my browser, but I can't find it again now.

AB#33935614