Nellie and Merlin, you have raised some issues which I find very interesting.
Merlin, are you indicating that once a person has been anointed as a King/Queen then there is no need for a second anointing? I can understand that concept within a religious context.
If Scotland gains independence, then there could be two separate nations with, in theory, two distinct monarchs even though the same person might be the monarch of each nation. At this point of time this is a hypothetical situation but, depending on the legislation enacted, this could be possible.
If so, then the situation would be similar to the reigns of James I, Charles I and Charles II. Each of these kings had 2 coronations, although I have no knowledge if each was anointed at the second coronation.
The political situation at the time made such coronations imperative especially in the case of James VI/I. The political situation changed dramatically when William and Mary ascended the throne as joint monarchs, and any attempt to have a coronation in Scotland might have resulted in armed revolt.
After the Acts of Union in the reign of Queen Anne, there was theoretically only one nation, and from that time only one coronation was necessary.
If the political situation changes, then it may again be politically expedient to have 2 separate coronations.