You have actually touched on a very strong trend in popular history and nationalistic reimagening of Newfoundland's war effort. There has been, in the last decade and a half a growing trend on the island and in it's cultural identity to damn the empire for the slaughter of the Newfoundlanders. One recent general history by a local author has gone so far as to outright state that on 1 July 1916 the British knew the day was lost but refused to give up and decided to attack once more but chose not to waste British soldiers and so sent in the colonials, ie the NFLD Rgt. Among his many historical inaccuracies, the author does not know, though more likely willingly overlooks the fact that the Middle Essex were ordered in at the same time as the Newfoundlanders.
Many popular histories, articles and documentaries are firmly entrenched with the mythic idea of the "lost generation." This plays into a growing nationalistic movement in which every thing bad that has happened to Newfoundland has been at the hands of the Brits and the Canadians, while every positive event was hard won by dedicated Newfoundlanders (usually Irish Newfoundlanders).
Likewise I have no time for such interpretations. Fortunately if one digs past the fluff you will find a solid, growing and imteresting discourse on Newfoundland's wartime experience. As for it being in Newfoundland's interest to participate, I believe more accurately it was in St. John's interest to participate. But your point is well made. It was a war that was well supported by Newfoundlanders and continued to be celebrated openly as a success until the mid 20's before remembrance took on a more somber tone. Yet in current popular accounts Newfoundladers were duped by the king and slaughtered for their efforts to please. At times it seems as if disillusionment writing is alive and kicking here. But what do I know.