We have discussed this above in the same thread. Incidentally, at the forefront "some people" you speak of is Sam Halpern, who has done extensive research on the break-up and written convincing articles and an excellent chapter in his Centennial Reappraisal book.I think some people recently have played the breakup down to a small and insignificant event. Lightoller thought the ship was at an angle of 60° when the lights went out. This definitely rules out a 10-15° breakup in my eyes.
What the various eyewitnesses saw as the ship breaking apart was the catastrophic culmination of an event that started between 2 and 3 minutes earlier. During those 2 or 3 minutes, keel was failing and the deckplates were being pulled apart but the two sections still were attached to each other. Also during that time, the sinking Titanic lost its longitudinal stability thereby greatly increasing the rate at which the bow dipped further and the stern rose.
I believe that Sam's calculation that the break-up started when the trim angle was between 11 and 12 degrees is absolutely correct, probably between 02:15 and 02:16 am. But that would not have been seen by any of the survivor witnesses, even though many would have heard the sounds of ripping metal which they described with various sound phrases, including "explosions". It was probably a minute or so later that the ship suddenly lost its longitudinal stability and gave that sudden forward and downward lurch which in turn generated the 'wave' about which several witnesses testified. This resulted in the rapid dip of the bow and rise of the still attached stern even though the break-up process was continuing. The lights failed at around 02:17 am and the stern had reached an angle of around 24-degrees before the final break-up and separation occurred 30 to 40 seconds later. That was what was seen and reported by various witnesses later.
As to Lightoller's report of the stern being at 60-degrees when the lights failed, you'll have to take it with a chunk of salt. It would have been difficult for him to judge angles of trim while soaked to the skin in icy water and balancing on top of an overturned lifeboat with several people even as others were trying to board. Remember that Lightoller also testified that the ship went down completely intact, something that we now know that it did not. Also, even expereinced sailors such as Lightoller would never have seen a spectacle like the 882-foot long Titanic sinking by the bow before and the 350 feet or so of the stern section sticking up in the air like it was would have created an optical illusion of a higher angle of trim than actually existed. Remember how many witnesses testified that the Titanic looked "enormous" during the final plunge? In the darkness, the 350 feet of the stern sticking out of the water at an angle of 24 to 25 degrees would have meant that the very end of the stern would have been very high from the sea level, thus creating an illusion of a much higher angle.
Of course, the 'perpendicular' stern came later after the break-up as discussed above.