Unless you are trying to count every single soldier in history as a mercenary, then you are wrong.
He was working for the Cuban government, on sanctioned actions to advise guerrilla groups in some of the poorest nations on earth. That’s very much not what a mercenary does. He fought against mercenaries in the Congo.
It’s also funny you need to bring up a person from 50 years ago to do your “whataboutism” on Cuba.