Cannot invoke functions from a JavaScript file with <script type="module" src="xx"/>

[CptGuo]

(Please fill out the issue template with your details)

Expected Behavior

The behavior of JavaScript methods can be rewritten.

Actual Behavior

If the JavaScript is imported with type=module, it cannot be referenced or rewritten, Removing type=module allows it to be referenced and rewritten.
Code example:<script type="module" src="testjs.js"/>

jscode:
function testfun1() {
alert(1111);
}

Specifications

• Chromium: ( 131.0.6778.85)
• TM: (i.e. 5.3.2)
• OS: (i.e. linux ubntu)

Script

(Please give an example of the script if applicable.)

// ==UserScript==
// @name MyName
// @namespace http://mywebsite.com
// @Version 1.0
// @description try to take over the world!
// @author Me
// @match http://mywebsite.com/*
// @require http://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js
// @include https://mywebsite.com/*
// @grant none
// ==/UserScript==

window.addEventListener('load', () => {
var fun = window.testfun1;
alert(fun); //Allways alert undefine
});