Ah, so Engadget's little infobox at the bottom is just wrong.

disordinary · on Sept 26, 2012

The infobox for the 808 says Symbian, the info box for the Lumia says Windows 8. Nothing wrong there.

warp · on Sept 26, 2012

The infobox shows symbian for the "Nokia 808 PureView", and Windows Phone (8) for the "Nokia Lumia 920".

The box isn't wrong, it is just confusing that the 808 info panel is expanded by default and the Lumia one is collapsed like the other phones.