I agree that this video is a good example of how turkeys react when they are alarmed about something, but are not quite alarmed enough to take evasive action. I refer to that sound as "concerned clucking/putting". Those birds have seen something they don't like and are letting each other know that they all need to be aware.
For beginning hunters, you certainly don't want to tree call to turkeys using that sound in an early morning roost hunt. It is not the sound of a contented bird that is just waking up normally. ....And if you hunt roosted birds that are making that kind of sound, you can be pretty much assured that they have seen something that they don't like.