I tend to lean towards the optimistic in my speculation, but, honestly, a PC version with all of these graphical features game would explain all these discrepancies.
- Delaying the PC release 6 weeks as From finalized the graphical features that didn't make the console version.
- Not showing any footage or information on the PC version during that time period.
- The immediate downgrade in visuals between trade shows in January and console footage in February.
- 60 FPS/1080p trailers/demos with all of the effects in place.
- Sconces placed throughout the entire game for the, now useless, torch.
Both the final console build and the PC TGS trailer have the exact same geometry and textures. What likely happened is From designed their game engine for PC/next-gen, then had to rip out many of these features last second for performance reasons. From needs some more time to finalize all of these features for the PC version that is releasing at the end of April.
This trailer is from mid-November though. Subsequent demos all the way up through January showed the same effects, footage, and areas.