The Norman Conquest is one of my favorite periods of history and I can not say that I particularly agree with you.

You are right about "Norse" being a bit of a buzzword, but it isn't entirely relevant as that particular usage is more or less the premise of this discussion and what the overwhelming majority of the people within this sub are referring to -- that being, Vikings & Norse mythology.

That said, and as I am sure you are well aware, the Normans were descendants of the Norse, Franks, and Gauls. While aspects of Norse cultured carried over, I believe they were quite distinct in their beliefs and culture. The Normans where overwhelmingly Catholic and motifs that come to mind (at least for me) would be things that are much closer to what most people would associate with things like Robin Hood or Arthurian Legends -- things like knightly cavalry, Romanesque castles, and a gold-crowned king wearing chainmail and a surcoat.

I'm not sure it would be accurate or particularly meaningful to describe them as "Norse." If anything, I think that even more nuance would be better and it would be nice to see people differentiate between the various European cultures associated with "medieval fantasy" -- as well as between the various periods of time they are actually drawn from (I think many people would even conflate things from the Dark Ages with things from the Late Middle Ages).

I also think far too many people conflate Norse and Celtic culture as well -- in addition to the Celts with the more contemporary Irish & Scottish Gaels, despite the Celts stretching back nearly two millennia earlier and spanning the majority of Central Europe. For example, I think many would be surprised to learn that one of the most significant archeological sites for early Celtic culture is located in Austria.