I am not the one making that distinction; section 23 of the charter does.
The immersion system was invented for anglophones. For specific historical reasons in Quebec, an English immersion system was not created for francophone students. You are probably more familiar with those historical reasons than I am. When one refers to the immersion system in Canada, one is referring to an immersion system for anglophones. There is no equivalent for francophone students in Quebec.
Parents who exercise their right to send their children to an English school in Quebec must have a specific connection with education in English. That restriction, those criteria were determined under Bill 101 in 1977. Section 23 was subsequently drafted, but with a Canada provision, in order to take into account Bill 101's criteria.