The seller must have MDSAP and to satisfy that, they need to show vigilance with any foreign based contract manufacturer. Although the manufacturers don't have to be ISO 13485:2016, it certainly helps your certification process if they are. Therefore, if the manufacturer only makes them for another company selling into Canada, only the seller requires the MDSAP. If the manufacturer later decides they want to offer their product into Canada, then they will need a MDSAP.
For example, we demand any foreign based contract manufacturer or supplier to hold a valid ISO 13485:2016 certificate. As a Canadian-based company, we must have MDSAP to sell our products in Canada. Fortunately, the FDA also accepts MDSAP, so it covers both markets.