All phones with 4G/5G worldwide should have it. They managed to make the broadcast push SMS thing used for the alerts a mandatory requirement for phones.

The broadcast warning from Japanese equivalent of NOAA don't get issued to areas where the peak acceleration is expected to be less than Shindo 4 level. So GP probably had 3 or less.

Shindo is peak and Magnitude is an integral, so these two can be wildly apart, and Shindo is more commonly used in Japan since buildings tend to be more resistant to longer events with lower peak intensity.