The stratus cloud is only generated if the visibility is below 2000m. Everything else makes no sense.
Here is a small code snippet.
if ((metarWeatherPhanomena.contains("FG") == true ||
metarWeatherPhanomena.contains("BR") == true)
&& metar.Visibility() < 2000 &&
m_settings->FSCloud_GenerateStratusAsFog() == true &&
FogCloudsHeight == -1 && m_settings->FsVersion() == aviation::enums::fsversion::FS2004)
{
}