Rivers of Light itself is an IP show, repurposing DIsney Nature film footage into its new narrative, just as Jungle Cruise and Nature's Wonderland repurposed bits and pieces of the True Life Adventures to create new experiences that become entirely new entities. People miss this because Nature Documentary Animals are not Marketable Brand Characters. You don't go on the Jungle Cruise and say "Look, it's the African Lion from the film "The African Lion"".
Reusing footage from Disneynature because it is excellent quality and Disney owns the copyright is a cost-saving measure, that does not make it a branded show. If it did, they would have cross-promoted it in a million other ways.