The reason, as always in such cases, has to do with a bug - quality control on software updates is hard, for sure, but it shouldn't be this hard to spot something so obvious. We're talking about the lock screen and touchscreen not working anymore after the update.
While we have always commended Samsung for how willing it is to roll out updates to dozens upon dozens of devices in a short span of time recently, stuff like this simply shouldn't make it to purportedly stable builds.
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