That is totaly hacked or homebrew. Also I think the sound is fake because the gba intro sound is not correct.
The sound being fake in the intro is an error in the emulation of the boot file. In other words, it always sounds like that on that certain emulator...
Man, theres the posibility that this is a concept to show to the excecutive board how halo could be in the GBA. Like the flat-shaded demos of sonic xtreme
I'll have to check again on monday but Vboy never sounded like that to me with the bios installed. As well I always used vboy in running some of my work (i am a comercial developer and vboy offers so many options for debugging a game vs the IS-GBC-Emu). On top of it the gba audio is only 8bit and I dont see how they could get halo sounds that good out of the gba.