You said “speaking for” the larger group. If, for example, we're talking about first nations, the majority of the population lives off reserve in urban centres. It would make sense if we're talking about that, so why would we close this off?
When you talk about 50% of the population, you say roughly 50% is male and 50% is female, give or take. There are groups that say they represent or engage with different segments of the indigenous population, whether they are off reserve in urban centres or not. We're talking about governance issues too. They might want a seat or even a voice at the table at this very important time, rather than leaving it up to a small group to set the stage for future discussions.