Why is this Undertale Song Unused?

Sources:

[lautarosilva]

"If he goes easy on us." As if Sans wasn't the easiest enemy.

[michaelkindt]

It could also just be a red herring put in the soundtrack so that you don't expect megalovania for Sans. Like, you just assume he's A normal battle, but then you find that you can't fight him at any point in the game. So you assume there must be A secret fight. Only for that assumption to be proven right, but it's on the no mercy route, and it doesn't use that song.

[noobfart]

oh, i thought this was about star ogg

this song was just a meme. its like "spoiling" with false facts. toby was very secressive with the no mercy route, going as far as replacing names, adding a warning and, not including many no mercy route ost in the official soundtrack

but its obvious, its getting a callback in deltarune

[SantiBolanos-wzte]

Maybe it's a play on Sans' character. He might fight you but he also might not.

[C____-]

I swear Song That Might Play When You Fight Sans has to be the closest thing we got to a canon Sans x Papyrus Theme and it slapped

[kawiuhs]

If Sans did fight you in the pacifist route, that’d be breaking his promise to Toriel. So I’m glad there was no pacifist Sans fight but I’m disappointed the song wasn’t used.

[nephew_alan]

"human, i remember you're SNOWGRAVES"

[PoyoPowerPlant]

I’m gonna reference the old “Megalovania is OUR theme” theory. I think if we were fighting Sans at any point where he was truly stronger than us, his theme would play (STMPWYFS). However, since we are much more of a threat in the geno battle against him, it plays Megalovania instead.

[EvilWafflz]

"Wanna have an unused song?"
"Sans"

[SY_]

In one of the interviews on the newsletters toby talked about a test fight where he said he had his friends fight sans in the Mettaton Hotel Resort
His friends said they dont remember that at all
This might have something to do with it
So maybe there was a pacifist fight after the dinner with sans which would make a lot of sense

[kaydensantiago]

Flowey RUNS away he doesn’t have legs and now my head hurts

[Bryce_the_Woomy_Boi]

What's even stranger is this song is in the ost, but not the songs from the Mad mew mew fight or the dog gambling room.

[Yuti]

It’s definitely a red herring, you beat the game, you look at the soundtrack “What, sans fight?!”, you try killing paps or something but sans never indulges you unless everything is at stake

[FounderOfCheese]

it's one of my fav songs in undertale!

[supermemoluigi]

well, i always thought this was a clear sign that in Genocide Route Megalovania is Your Battle theme and You're not fighting Sans, Sans is fighting You.

[Embrusp]

Yeah! I’ve been wondering this for so long but no one has answered it online! Thanks a lot!

[Bolufo]

Oooohhh! Of course! Toby could totally use STMPWYFS in Deltarune, just like he used Before The Story!

[Sporaticzzz]

I always figured it was a pacifist sans theme due to it being comically dramatic for a sans related song along with the inherently goofy name it would fit a non serious sans fight

[Potato]

My theory is that megalovania is the genocide player's theme because they are the evil one and therefore the one with battle music

[Michal-jehx]

Due to its location in the soundtrack, I have the impression that it was supposed to be music for fighting Sans on neutral, but Sans is too lazy