There would be a separate distinction that the federal government would put into the housing strategy for urban, rural and northern indigenous people in general. Given that they are by far the largest group in those four groups, it only makes sense that they would have a separate distinction.
Also, there's been 40-plus years of urban native housing experience with all those housing providers in the country. There are well over 100 of them who have created, developed and nurtured communities over that period of time. If suddenly that were to stop and be taken over by one of the other three entities, then it would be like rebuilding and reinventing a wheel that already worked fine.