I recall reading that there was a project in the Pentagon to review MOH recommendations that were downgraded in the past for reasons unrelated to the action. For example, some minorities, Jews, and awards that were downgraded “because we only awardedX number of MOH for that theater.” The recent awards that are really old are a result of that review.
Also from the article:
'Spc. Donald P. Sloat was awarded the Medal of Honor for his actions in using his body to shield comrades from a grenade blast near Danang, Vietnam, in January 1970.'
As you said, really old.