Your best bet to learn more is to read Japan-only guides such as perfect works and look up old gaming magazines. We found out that Saga Frontier used an event editor/interpreter to write and perhaps incrementally develop event scripts from a photo of it in an old Japanese gaming magazine. Granted the way they are organized it is ludicrous to develop them by hand, but it was nice to see an old theory vindicated.
Japanese forums and wikis usually have more info, that's where I would start.