You're not wrong about Explorer, but the parent is also partially right.

While you can move, resize, minimize, maximize, and switch between windows without Explorer running, other window management features are limited or nonfunctional without it:

1. Explorer is responsible for the taskbar, and thus the only useful way to view minimized windows.

2. Alt+Tab still switches between windows without Explorer, but the window switching UI does not appear.

3. Virtual desktops still exist without Explorer, but there's no obvious way to switch between or otherwise interact with them.

4. Snapped windows retain their positions without Explorer, but window snapping functionality is not available, and resizing snapped windows does not resize adjacent windows as it normally does.

5. Without Explorer, desktop backgrounds and desktop icons do not appear.

5. Explorer is responsible for handling many system level keyboard shortcuts, including shortcuts for features not obviously related to Explorer or missing window management functionality (e.g., game bar, snipping tool, emoji panel).

As a reminder, the topic is Wayland, and the great great great great grandparents post was referring to rendering/compositing systems DWM and Quartz as architectural equivalents to Wayland in the major closed source operating systems.

The parent, misunderstanding the discussion on compositors, diverted to a discussion about user interfaces. It's an understandable point of confusion given that Microsoft chose to name their compositor “Desktop Window Manager”, when the term “window manager” is typically scoped to user interface.