Hmm, it's not in the pack for Treasure of Aht Urghan either. Generally, when a track is missing from a PSF2 set (or some other xSF sets), it's because that track is streaming audio such as would be playable in VGMstream. Most of the time, these stream files aren't included in xSF sets due to their size, and it is/was kind of unofficial etiquette to leave them out when you create and distribute a set. The size and bandwidth isn't quite as much a problem these days, but a lot of sets haven't been updated to reflect this, or if they have, they are distributed via methods like the tracker.
From a Youtube video, "Ragnarok" doesn't really sound to me like it couldn't be achieved via sequenced music, but I might be wrong (it's obviously not always an accurate way of figuring out if a track is streamed or sequenced).
It's also quite possible errors were made in the creation of both PSF sets. xSF sets can range wildly in how difficult to create - it can be as simple as using Saptapper to automatically rip a GBA game that uses the Sapphire music driver, or it could be something that nobody has managed to figure out like the Procyon Studio driver found in some DS games. Even a game that has seemingly been properly ripped, like the FFXI releases, can still be hiding stuff in one way or another for various arcane reasons.