"A blade to smite the gods."

I feel like people are overlooking this line, or maybe I am looking too much into it.

In 3H, the people of Fodlan did not know the Heroes' Relics were created to wage war on the gods. This phrasing makes it seem like Dietreich does know their purpose, but perhaps not exactly how they were created, or else he would not bring a weapon powered by a Nabataean heart to a contest hosted by (seemingly) a Nabataean sovereign.

If it is a sequel, then Fodlan has learned the truth about the weapons (I forget which route it is fully revealed, I think SS and VW?).

If prequel, then not enough time has passed for Rhea to fully re-write history to make all the weapons be known as gifts from the gods.