It isn't that governments do not have to have secrets. Things like military plans, codes and cyphers, even ongoing diplomatic initiatives can be properly kept secret. But much of what is "secret" is actually only 'embarrassing". Anything concerning events 40 years ago cannot be a threat to current military plans, codes and cyphers, or ongoing diplomacy. It can only be embarrassing.
Saudi-led planes hit Houthi-controlled government buildings (Reuters)
from the article: What happened to Charles Jordan?