Even though I prefer Yub Nub, I do think Victory Celebration better fits the bittersweet ending of the trilogy, especially in the context of the prequels, in which, let me remind you: the main character gets BURNED ALIVE IN GRAPHIC DETAIL. In the context of 1983, though, I definitely agree with Mocata that it sounds out of place.
It turns out the reason it sounds like “90s new age” is that the temp track was taken from the soundtrack to this TV documentary series called 500 Nations. It aired in 1995 and sounds typical of History-Channel-type documentary background music from the late 90s and early 2000s.
https://www.youtube.com/watch?v=pler4cr4yxo
There’s something oddly charming about synthesized generic new age being played by a live orchestra, though. I mean whatever, it still somewhat fits the tribal setting I guess.