I think this goes back to the answer we've already given.
In contexts where the term “Indigenous governing body” is used in a bill that applies to all ranges of indigenous governments—these could include bands, councils or the different forms of indigenous governments we see across Canada—a definition can capture that range.
Here, that term is being applied in context. We're not talking about all types of indigenous governments. We're just talking about these Métis governments, which are a type of indigenous government. There's no need to capture that breadth of other possibilities, because it's simply not relevant to the bill.
To your question, yes, there's an understanding of what this means here. It's spelled out in that paragraph. They're authorized to act on behalf of the collectivity. That's what it means to be an indigenous governing body.