Depends on what you mean "tied to the lore." The previous Omega raid bosses were legends, myths, and faerie tales in the XIV universe made manifest by Omega. They just happened to be enemies from V.
I fully expect this to be something like that in Sigmascape as well. Other bosses from previous FF like Goddess, Fiend and Demon are a little more intricately woven as gods of Meracydia. It varies, really.
Also I'm surprised with how many people think a character named Brutus is going to betray us and not his Emperor...
