The defined zones immediately refer to the first official language spoken. That's how we define the strong presence of a francophone population.
If I understand correctly, you're suggesting we use the potential demand for services in the minority language variable instead. This variable came out after the census. It's not about defining the population, nor is it an identity dimension. It's really to be able to estimate the number of people who might want to use federal services in the minority language.
If I understand what you're saying, instead of referring to the first official language spoken, or FOLS, as it's commonly known, you're suggesting we use the potential demand variable instead.