Although article 32.5 doesn't specifically mention the UN Declaration on the Rights of Indigenous Peoples—and certainly this is something that the Assembly of First Nations, other indigenous groups and peoples were saying and continue to say is very important to have integrated into the agreement—there is, in the footnote, some language or text that allows for some flexibility and I think extends the exception beyond section 35.
The footnote says, “For greater certainty, for Canada the legal obligations include those recognized and affirmed by section 35 of the Constitution...or those set out in self-government agreements between”. That's the footnote that clarifies it for Canada, but the actual article talks about “legal obligations”.