Interesting situation. Though other companies over the years have sought the Buck Foundation's permission, I really wonder just what kind of rights the Foundation even really has. If the catalog was acquired in 1970, there was no federal copyright for sound recordings at that time, just a patchwork of state laws against selling pirated counterfeit copies, mostly. In other words, the Buck Foundation may have for years been asserting a right they didn't even really have. I know of record companies that have tried that and gotten away with it lots of times -- asserting copyright they did not even really have. (There ought to be a law against THAT. That's tampering with the public domain, to put it politely!) Just because you get away with asserting a right does not necessarily mean you have it, even with the best of intentions and non-profit status.
Most likely, though, White and Revenant just didn't do their homework on this or made bad assumptions. That'd be a shame.