Strange the page does not describe the "metric second" then, since it is not the same as the SI second. I thought that the second was the unit which was the sa

Strange the page does not describe the "metric second" then, since it is not the same as the SI second. I thought that the second was the unit which was the same as in SI (=metric). But then it is not the same as the SI second, so not metric at all. Very confusing.