That's interesting, is there some account of the circumstances of these recordings? Were they held captive or something?

I didn't see an account, but it wasn't exactly a rare event to force the issue. The other possible cause for caution is the recent backlash against Universities' interaction with the tribes. The biggest culprit is using data about the tribes to write grants to provide services on the reservations without input from the tribes (or finding out if they are stomping on the tribes or tribal entities own requests). It has instilled a sense of caution in a lot of organizations.