The term "revolution", while it does not have to imply bloodshed, does imply some kind of struggle involved. My point about what happened in the countries of Eastern Europe when the Soviet Union fell was that there was no struggle at all, not even a bloodless one. Everyone just said "about time" and went about the business of running their own countries.
This is absolutely a case of survivorship bias.
In other words, if the actual facts had been different, we would use a different word to describe what happened. Yes, indeed. That's why we have different words: to capture meaningful differences in the facts we are using the words to describe. If we simply called every change in government a "revolution", the word would be useless.
I think that's rarely the case, at least not when the people starting the revolution are reasonably sane (by which I mean they have a reasonably good grasp of reality and use that to guide their actions). I think the people in Eastern Europe who started "revolutions" when the Soviet Union fell had a pretty good idea that little or no bloodshed would be required.
It's quite possible that the people who started the French Revolution didn't realize how much blood would be shed, but to me that just means those people were not reasonably sane. And there is plenty of other evidence that they were disconnected from reality.
(By contrast, I think the people who started the Russian Revolution, and the Communist revolution in China, were well aware that much bloodshed would be required, and they were perfectly OK with that. That makes them reasonably sane by my definition, but it does make them "insane" by other definitions--psychopathic or sociopathic, for example.)
If we get to simply exclude all of the successful and largely bloodless ones, then of course revolutions are messy and risky. It is that way by definition!