This might be an odd question, but when or why would you use this button? The leather cover for my key, bought in Japan covers the button, but has embossed areas on the leather for the other buttons!
If you park and lock with the roof open then the internal sensors are likely to trigger due to movement in the area above and around the car. Anything from people looking in to low flying birds.
Pressing this button will disable the sensors but the alarm will still trigger if anyone were to open the doors.
If you’re on a cross channel ferry … use this to stop the internal motion sensor setting the alarm off every time the swing ticket (hanging from the rear view mirror) moves a bit or a coat slides off the seat etc. After a 5hr crossing you may have a flat battery. I’ve seen it happen