Pausing for a second, going back a second in time or changing how long a second is all are hacks that are bound to cause some edge case failure somewhere. I'd like to see a minute have a 60th second just as February has a 29th day.
The Earth's rotation is slowing, but it's not a steady process. For example, the Boxing Day earthquake in 2004 permanently decreased the length of the day by about 3 microseconds. Here is a graph of the changes over the past few decades:
https://upload.wikimedia.org/wikipedia/commons/5/5b/Deviatio...
Also, given all that variance and the fact that we only seem to be shifting around 1 minute per century at the current rate, we probably could get by having a leap minute every few decades when necessary.
This works fine for any system trying to interact with other computers and humans while keeping consensus on the time. Any system that is trying to determine earths yaw would no longer be able to rely on F(time), but that is only a minor inconvenience.
The complication is just that there are a whole lot of systems out there that assume that every minute has exactly 60 seconds with no exceptions, so you end up with crazy workarounds like smearing to hide that 61st second from such systems.
It's different because you don't have to keep track of what an authority is saying or deal with the actual time adjustment except once in a century. Once in a century is acceptable since we will only deviate by around a minute at our current rate.
The problem with leap seconds is that time is often represented internally as seconds from the Unix epoch, and this simple integer counter assumes leap seconds don't exist. In effect, there is no way to actually represent a leap second in many computer systems, so the question of what you do is basically a choice of the least painful lie. Handling leap seconds in the situations where people care about them requires a lot of complexity for an event that happens only once every few years.
There's a movement to abolish leap seconds, which I am very much in favor of.
It clearly isn't since the original post highlights three different ways people adjust the time making all these organizations lack consensus on the time.
Move to leap hours, and by the time it's needed, let the AIs sort it out.