The point is not that time synchronization is inherently bad, only that it's usually not the correct thing for a distributed database to resolve update conflicts with.
Yes I completely agree. I fail to see how anyone would think that using a clock as a source of truth in a distributed system would be in anyway a good idea. As far as PTP it would be too expensive to deploy at large scale which was some of the motivation (i believe) behind truetime.
They are when you know that the leap-(nanosecond/second/minute/day) is coming up. When you know it is coming, you can "smear" the time difference over, let's say, the entire year, so when it happens, every system behaves correctly.
