I've been fixated on this question for a while, but I finally found a mixed answer from the man himself. In
Spiral Mountain re-mix, after the Gruntilda's Lair section, is it
Gobi's Valley (part right after the introduction) or
Mayahem Temple (introduction of boss' theme)? To me it sounds just like Gobi's Valley, and the violin instrumentation gives me desert vibes, whereas everyone else is saying Mayahem Temple. Grant corrected someone saying it was Gobi's Valley, then a fan corrected him, and then Grant conceded saying he's probably getting old.
To me, they both have a very similar melody, so it could technically be either one, and I think it's Gobi's Valley because a) the violin and b) makes sense for all those quotes in that section being from the first game. Any thoughts on why one but not the other? It's an open question, since even Grant himself is unsure--and if anybody would know definitively, it would have been him.