imho his TL;DR is better than yours, but your improvements could be made to his. In my education we was taught that in science and business, the abstracts should tell the whole point of the story; the "spoiler" should not be saved till the end even though that makes for more fun; this is to allow a busy person to get the takeaway quickly and assess if they need to read all the detail. Whether anybody agrees with that or not, it's been burned into my way of looking at the world, so even when reading this article, all the way through I was gritting my teeth thinking "I wish I had some clue as to what I'm reading about."

so to add in your point, to his TL;DR I would put in "the intial dataset included only the trains that had suffered the fault, but as the fault was caused by a functioning train, a more comprehensive dataset was necessary to find the problem; had it been provided initially, less detective work might have been necessary"