In short: Crytek have spent so much time thinking about how best they can show Korean gentlemen being throttled, they forgot to remove the design-doc-script thing from the demo files. Oh noes!
Basically, if you want to know all this stuff, you need to head to “C:\Program Files\Electronic Arts\Crytek\Crysis SP Demo\Game\Localized” where you’ll find the english.pak file. Open it up with winrar or something. Inside the compiled docs bit you’ll find an enormous amount of 27 (Count ’em!) pages of plot based gubbins – and new screens – which you can absorb at your leisure and be able to tell people that the cake is a lie, or local equivalent thereof.
Thanks to Thiefsie for the tip off.