The reason you're seeing such a variation is because the icons are based on per-country map conventions. They have different icons for use in different areas, f

The reason you're seeing such a variation is because the icons are based on per-country map conventions. They have different icons for use in different areas, for example there are some specifically for Japan. Christianity is covered in the generic "Church or temple" icon, but people in other countries with other major religions wouldn't recognize that iconography. The point is probably to be open to other religions in the West, while also considering the breadth in other countries.