Well I thought it was wrong when it was said, I have done very limited research on it and it does seem to be the case if you are from a country with a decent Health system, and you don't leave the Canadian Health area after clearance.
The doctor concerned is an Immigration specialist, I was able to get an appointment with them at a days notice, as that seems to be all that they do (must be good money in it), so I would surmise they know the medical rules side of things better than me... and I did not ask the question, they told me.
That's why I state the doctor told me...I'm happy to believe it, but if asked to do another medical I wouldn't be that upset.