The point from the article is that the NSA doesn't permit 'password of the day' style encryption - it's all or nothing.
For the operational requirements of the predator, nothing was better than all. They'd prefer an intermediate option, but it isn't available until procedures change.
I get that. It just seems kind of perverse to transmit in clear because scheduled encryption has risks of its own. Last time this was posted I mentioned that while interception of drone video by the Taliban or whoever is probably not that big of an operational threat, bigger strategic competitors like Russia and China have probably accrued a good lot of intelligence by amassing such data in quantity. Perhaps the NSA's thinking is that this is less critical than exposure of dynamic encryption models to the wild.
For the operational requirements of the predator, nothing was better than all. They'd prefer an intermediate option, but it isn't available until procedures change.