Child window may cause undefined behavior on macOS

Adept the examples here:
https://www.qt.io/blog/window-embedding-in-qt-quick

import QtQuick
import QtQuick.Controls

ApplicationWindow {
id: mainWindow
width: 640
height: 480
visible: true
color: "black"

ApplicationWindow {
parent: mainWindow
width: 400
height: 400
visible: true
color: "white"
}
}

Run this and there will be a warning message ouptut:

appChildWindowTest[12350:146896] CoreAnimation: setting `contents' on CAMetalLayer may result in undefined behavior

For a such simple example, this warning seems to be non-fatal and harmless. Both windows are rendered correctly. Although I am not sure if it is going to cause further troubles in more complicated project.

And judging from the name "CAMetalLayer" I think it is an Apple-exclusive issue.