I believe his point was that it was transformative for the elites (who are the one writing history) but not so much for society in general. A refreshing point of view; I also believe we tend to inflate the influence of war and politics and agency really in history.

If that was their point, then their point is completely wrong in the context of the War of Hastings.

Do you and the GP really not know anything about how William/Guillame's victory tranformed England, for everyone? The very language we're writing in at this very moment is a direct consequence of that victory.