If the question is as to whether a manufacturing-related problem could have caused the problem, then I can perceive (but only in the absence of any specific knowledge) a circumstance whereby torsion might be applied during the layering of the unit's parts (eg. let's say warping of the bed in which the substrate perhaps sits) which, while not causing breakage, might mean that a "knock" or pressure at some time in the future, of far less than that which normally is required or expected, might push the screen past its tolerance to cracking. Unlike the delicate glass ornament, the ebook device undergoes far more handling and varied circumstance.
However, as to whether this is a position that can be successfully argued against the manufacturer/seller of the unit, who would almost certainly suggest from their position of knowledge of said manufacturing process that this is not the case, well, as you say, Harry, I suspect this is "very unlikely to happen".
This does not mean, however, from the original poster's advice of the circumstance of the breakage, that I do not wish them success in their endeavour to claim under warranty.