That is not true in this case, or even in general.
Canada trades with Cuba, but is not restricted from trading with the United States.
For example, you can freely purchase Cuban cigars in Canada.
Another example: the U.S. had an embargo against Iran for many years, but that didn't stop Siemens in Germany from selling them uranium centrifuges, nor did it result in a U.S. embargo against Germany.
Edit: here's a Canadian government site encouraging Canadian companies to do business with Cuba.
https://www.tradecommissioner.gc.ca/cuba/index.aspx?lang=eng