Well, the way I see it, you gotta think of it like Shovel Knight in a way - the Game Boy-inspired sound is certainly not gonna be present on your average Game Boy cartridge, but it's a fantastic use of its original instrumentation to invoke nostalgic vibes - though in Shovel Knight's case, it's a bit more authentic in a sense as while the sound effects do not interrupt the songs at all as it would on an NES, it was all composed on Famitracker within the limitations of the VRC6 chip. With enough effort I could imagine someone backporting Tower of Heaven's soundtrack to be playable on Game Boy hardware in some fashion.
Ah yeah, the intro is cut off because that's the mix they used specifically for Brawl (and Smash 4). Perhaps you were looking for this version?
To be fair, having completed that game myself, I can see why people would regret purchasing it. The worst part is, the biggest reason is a HUGE SPOILER for the game itself so you can't even discuss that with people! Though I haven't played it, I hear Bravely Second is better about that...
