They did not visit Cuba in 1971.
It is thought Castro met them in the Caribbean in April 1971
https://www.reddit.com/r/Snopes/comments/7zidq8/snopes_made_a_mistake_regarding_trudeaus_april/
It's possible. But do we know whether Fidel felt secure enough in leaving Cuba and letting Raul hold down the fort while he's out of the country?