Don't know exactly as never been involved but don't most of these "bequests" come about as a response to death / inheritance tax and a means for a family to retain a home albeit with restrictions on their former freedoms and the need to accept "visitors".
Recent TV prog had a property on their that they had taken over as family could not pay taxes and NT was a way of staying "in residence".
Would be a little surprised if they all left property to NT as they were so good? I used to be a member and found the organisation was on occasion blooming awful.
P