Oddly enough, Cameron's 2012 "re-imagining" is somewhere between what he depicted in his film and what was thought in the late 1980s in the first 2 or 3 years after discovery of the wreck. In those days there was a lot of talk about how the stern got vertical and 'swung around' after the bow section separated and fell away; there are some good illustrations to that effect in Eaton & Haas' first edition of Titanic: Triumph & Tragedy. By the mid-1990s, the thinking had changed and they believed that the bow did not separate completely after the break-up but was still connected to the stern section at the keel underwater. This is depicted in Cameron's film at the start, when the contemporary explorer in the submersible illustrates how the bow pulled the stern section down by the keel, thus causing the latter to become nearly vertical before dropping back. There was no mention of the swing around.
As you have seen in the 2012 reconstruction, the initial break-up occurred at a relatively low angle and the bow section fell away without pulling the stern upright. The, as the sea flooded the exposed deck spaces of the stern, it listed sharply to port, started to sink and swung partly around at the same time. You can see that after the stern had sunk about halfway in that manner, the movement did make it briefly vertical.
But looking at that 2102 reconstruction makes me wonder how on earth Baker Joughin managed to hang on to the end of the stern through all those movements. If he really managed it, it must have been an experience to surpass the scariest of present day Grade 5 rollercoaster rides.
