I don't think that it's true. According to the reports that we have on immersion, around 50% of immersion teachers went through the immersion system.
I personally teach French as a second language here in Ottawa. I've taught core French and immersion. I must say that, despite what my current level of French may lead you to believe, I lacked the confidence or linguistic security needed to teach in a French school in Ottawa. I felt quite comfortable in my immersion class. However, I would never have had the confidence to try to get hired by the French board. Admittedly, I didn't have the chance to fully live in French. My mother was Irish and I learned French. Of course, a person could be confident enough in their abilities to teach in a French school. I applaud that person!
That said, Mr. Boulerice, I don't think that the figures reflect the reality. I think that the figures may be more accurate in remote areas, where people are happy to welcome a French speaker, even though that person took an immersion course in a French school. People are happy to be able to provide the program.
Moreover, the skills are different. When I teach a second language, I use a different methodology to teach the language to a person who has never spoken it before. Francophone students will have an ear for French, as they say. Anglophone students can't yet tell whether we say “le table” or “la table”. We must use teaching strategies to help them hear French properly. I'm personally qualified to teach French as a second language in an English school. However, I'm not qualified to teach French in French schools.