That's not entirely accurate. It means that "rights", not the treaties, that weren't extinguished before 1982 continue to exist. There's a difference. These sections apply to modern treaties also.

The Royal Proclamation is part of the Constitution and gives extensive rights to First Nations. Namely:
- recognition of aboriginal nations
- recognition that First Nations have communal (as opposed to individual) rights on their land
- First Nations lands are alienable to the Crown only
- obligation of the Crown to protect Indian lands
- requirement of First Nation groups' consent in a public setting to alienate their land 

The Proclamation also gave extensive rights to the "Canadiens" (as the French Canadian ancestors were known then). After conquering New France the British were trying to appease competing factions (Canadiens, American colonists, and various First Nation groups). That attempt failed obviously with the American Revolution.

Anyway, the Proclamation still has legal force.