Firstly I doubt that.
But, to answer your question, the reason this is possible is because a console is a 'fixed' design. ALL consoles of a given type are the same.
This means developers can use every trick in the book to squeeze more performance out of a console, confident in the knowledge that any trick they come up with will always work correctly.
No two PC's are identical, so you can't do this in any real meaningful way on a PC.
Add to this that the operating system which allows you to do so much with a PC does a lot of things in the background that are important, but not strictly needed if the only thing you cared about was playing a game, and you find that a PC probably needs to be about 4 times as fast at the very least just to look 'the same' as a console game.
However, I should note from personal experience that I can (and do) run PC games at settings that a console couldn't even dream of handling.
2560x1280 is a weird resolution, but running games that way at 40fps with 4x AA and 16 anisotropic filtering, plus realtime shadows and very high resolution textures...
May ironically not look that much more impressive than a console game, but compared to 30fps at 720p (1280x720), usually with tricks to hide the corners that are being cut is likely to take only about 1/5th the processing power even WITHOUT taking the inefficiencies of the PC into account.