Same! I distinctly remember seeing portions of this wallpaper that led me to believe it's procedurally generated and not simply a collection of video files, and had to rewatch it to confirm. There are several points where the date and time match the system date and time down to the second.

It features the current date and time with seconds, so it must be rendered on the fly.

The assets and some? of the scripting for it are in a bundle at:

/System/Library/ExtensionKit/Extensions/WallpaperMacintoshExtension.appex

Can see the time and date being added here I think:

System6ControlPanel.program

    //
    //  System 6 Control Panel
    //  Macintosh 40th Anniversary
    //
    //  Copyright © 2024 Apple. All rights reserved.
    //
    //----------------------------------------------

    start simultaneous
        scale out
        let image = "System6ControlPanel"
        ...
        ...
        add time at 267, 165 name "Geneva12"
        add date at 274, 239 name "Geneva12"
    end simultaneous