While it may be true that progress in technology is accelerating, what do any of the data points at or before the one labeled "Homo sapiens sapiens" have to do with progress in technology?
The reason the chart has no objective meaning is that "Event" is unspecified.
Well I suppose that's true in the case of this posting but it is not true of the chart in the book.
The author makes the point that the actual "events" that are selected are not that important. You can pick any set of events that you like that represents significant milestones in terms of the advance of technology. His point is that these events or milestones are coming faster and faster.
Example: How many years did it take for us to go from kites to balloons to gliders to gliders that would a carry a man to a plane that was self powered to a man on the moon. Chart those events and you will see that progress accelerates. That is the point of the chart.