Very interesting and for a couple of reasons, I believe it works.
The Royale has basically the same feature set as some G-Shocks (like my GD-100 and GD-400) and at least another Casio (the DW-291). The G-Shocks have both the flash alert and auto backlight. The Casios don’t.
For industrial production reasons, it’d make no sense for Casio to re-draw all the circuitry for each specific model. For market placement reasons, it makes very good sense to reserve some features for the more expensive Gs while keeping the “lesser” Casios less feature-rich.
Try the LCD screen test procedure. On the last screen you get what many claim is the firmware number, which sometimes coincides with the module number, but oftentimes doesn’t. That, in my opinion, “proves” the circuitry is the same. So connecting something that is unconnected activates features Casio decided to reserve for other models.
I don’t have a Royale anymore, but I did and I can confirm it has the same firmware number as the the GD-100, GD-400 and DW-291 show in the pic below: