I’m going to tell you a true story, one that’s shocking and going to terrify you:
The past three new Fire Emblem games have made the final map theme the theme you hear while facing the final boss/enemies.
Let me emphasize it a bit more.
Past. Three. New. Fire Emblem games. The final map theme plays instead of an individual theme 🙂
Ok, ok, I’m gonna stop playing around!
So, Fire Emblem games, starting from the very first one to Fire Emblem: Path of Radiance, have had the standard boss theme or final boss theme around on the final map. You get to the final map, you move your units around, and enjoy the theme of that map. Then it changes to the battle themes once you engage with a unit. However, that process for some reason has changed over the past couple years!
“Walters, Echoes had individual themes play in the final map. Shadow Dragon and New Mystery had the same. WTF are you talking about?”
Well, I DID say new Fire Emblem games.
It’s actually fair to not realize this because I actually forgot. You think this started with Awakening, where ID: Purpose plays as the overall theme, and Fates ended up doing the same.
…Radiant Dawn, however, started it first!
(and I should add, it is a glorious theme)
Radiant Dawn, the sequel to Path of Radiance, came out in 2007. Since then, the order of Fire Emblem game:
Fire Emblem: Shadow Dragon (Remake)
Fire Emblem: New Mystery of The Emblem (Remake)
Fire Emblem: Awakening (Not a Remake)
Fire Emblem: Fates (Not a Remake)
Fire Emblem Echoes: Shadows of Valentia (Remake)
Fire Emblem for the Switch (100% not gonna be a remake since they said NEW)
So, we can presume the Switch version is gonna make the Final Map theme the overall theme. And…and…I’d like it to stay that way. This isn’t to say having those boss themes and such are bad since FE music is awesome. But when listening to that Final Map theme in Echoes…it was awesome. And then I go and face Jedah. Or Duma. I think it’s just smart honestly. I dunno who made that change, but I think making the Final Map themes the overall song for the last chapter is a good decision, and I hope it sticks around, personally.
FIRRREEEE EMMMMBLEMMM! 
I never realized just how good Radiant Dawn’s final map theme was until now.
Yeah it’s really great right? You’re pretty much focused on beating Ashera so I get it might not be a factor, but it’s pretty impressive as a stand-alone when you’re not battling.
Actually, the final boss in Awakening had a seperate theme from the rest of the map, “Monstrosity” I think.