Eurogamer has a new article with an update on the downgraded graphics.
More information.UPDATE 21/03 2PM GMT: A Forbes reporter heard more about the issue from a source close to development.
It all boils down to "playable framerate", apparently. "The early builds that the screenshots came from were playable but only just so," the source said. "The game was not in a state where it could be sold at that point. I strongly suspect that they were focusing heavily on delivering a top-notch experience on PC and underestimated the challenges the new systems would pose on PS3 / Xbox360."
"I sincerely don't think they intended to deceive, but in the end they sacrificed a huge amount of graphical fidelity at the very end of development because they couldn't resolve the framerate in any other way."
The footage and trailers From Software used, it did with best intentions, unaware of the sacrifice it would later have to make, the source propositioned.
"The game would have been much worse without the change (as in, many would call it unplayable and broken.)"
Theoretically, such issues could be resolved for a PC version, and Bandai Namco told Forbes we'd hear more about that version in April. The forward-looking engine would also shine on PS4 and Xbox One, From Software told IGN earlier this year, although no next-gen versions of the game have been announced.