I'm quite sure that some Mexican officials - in their 20s and 30s in 1963 - are still around. Not in government but still alive. You can redact names and still figure out who they were. They were promised anonymity; that doesn't end when they leave government. Especially if they were given money or bribed or broke Mexican/foreign government law. If you promise people not to reveal their names in return for help and then reveal them don't be surprised if nobody helps you in the future when you ask them.
Come on Steve. Do you really believe the current Mexican government doesn't know who those people were?
Same for the Russians. Secrets like that can't be kept forever. By now the Mexicans, Cubans, and Russians know who was working with the US in the 1960s.
Secondly, the entire geopolitical map has changed in the last 60 years.
Fidel Castro is dead. His brother Raul is no longer in charge.
The Soviet Union is long gone
The only consequence of naming names of people who might still be alive are domestic politics. We can be certain that they have legal immunity if they worked for US intelligence but in the court of public opinion, some Americans might suffer depending on the nature of what it is they did. If there are no crimes being covered up, what do those people have to worry about?
Thirdly, the CIA is still fighting disclosure of files involving CIA agents and assets who are long deceased. Which makes even less sense unless there's something nefarious or embarrassing in those remaining files.