Eh, if you're gonna link a Reddit thread on it, you may as well just invite /u/tokyometal to this forum and have 'em answer directly - they're effectively the only authority of the underground metal scene over there.
My initial comment was moreso based on the number of limited releases that Japan's gotten from metal albums over the years, coupled with touring there being more complicated - so when bands _do_ get to tour over there, it's usually a crazy good show. Drives demand, etc.