Whew, that drew me in more than I thought it would. If I didn't know any better, I'd say the ENTIRE game text is in there. Quite astonishing that it's just sitting in the ROM, alongside the Japanese, and it's still only a 2MBit cart. Not gonna lie, I'm interested now.
Wouldn't be the only game I've seen that.
Equinox/Solstice II for the SNES has both Japanese and English localizations stored in both the Japanese and US (and presumably PAL as well) ROMs, meaning they were both developed together. (although only the Japanese version got a scrolling prologue telling you the opening story, for the English release the backstory was relegated to the manual)