I see what you mean but I dont think youve quite put your finger on the problem It seems to me that the later use of the term is a kind of long tail trailing from the mediaeval usage so I dont find  it a problem talking about the former in an article about the latter any more than I see it as a problem talking about film adaptations in articles about books But youre right that there is something wrong with the hatnote The problem is that by saying This article is about the historical Principality we imply strongly that there exists a later principality which should be covered in some other article But there isnt theres just a tail of usage So youre quite right that we need to change the hatnote though not I think to  is primarily about which still implies that theres some other principality But then do we even need the hatnote at all We already have as the last sentence of the introduction The term principality is sometimes used in a modern sense to denote all of Wales but this has no constitutional basis Is it too much to hope that a confused person will read that far If it is too much to hope then what we need to change in the hatnote is the definite article which is what implies that there exists some other Principality of Wales We could do something like this This article is about a historical entity  For use of the term Principality of Wales to describe Wales after  see below Or even The Principality of Wales existed from  to  for use of the term to describe Wales after   see below