Yes, the shackled skeleton's remains are new evidence of horror, because we're only beginning to understand how barbaric some societies were. Our modern societies are very civilized compared to the horrors that occurred in ancient civilizations. No doubt, this unfortunate person is just one of many people who died under tragic and terrible circumstances in these societies. We need to learn from the past.
For the sheer fact that the 80 skeletons found in Greece by archaeologists were shackled, I have to agree that they are evidence of a horror we were not previously aware of. I feel my opinion is further evidenced by the fact that the bodies all appear to be of young people who were in good health at the time of execution.
The ancient world was often a brutal place to live. Finding some skeletons is not really evidence of anything that we were not already aware of. To act astonished that people long ago were killed in which we may find unsettling is a bit naïve on any one person's part.
No, the shackled skeletons recently discovered in Greece are not evidence of a new horror. It is in my opinion that the shackled remains of humans are examples of the violence and power that humanity inflicts on one another still today. The discovery reminds us all that freedoms cannot be taken for granted.