S650 Mustang 4-door?! Design sketch raises questions

Credit where it's due, I saw this first on Motor1 - Official 2024 Ford Mustang Design Sketch Imagined A Sleek Sedan

If you look at the bottom left corner of the image above, there's a 4-door Mustang among the official design sketches from Ford.
What could it mean?!!!!
Was this the rumoured hybrid? Is it a future EV (like the Corvette and Camaro rumours), or maybe it was just a "What if?"
In any case, I'm intrigued. I've seen Mustang sedan speculation going back at least 20 years, but figured the Mach-E was probably the culmination of that. I don't think we're going to see a 4-door variant of the 7th Gen, but maybe there's one on the drawing board for Gen 8?