The input saudiArabia geojson is invalid because it's wound the wrong way. According to the spec polygons must follow the right hand rule.

The winding is likely being fixed (reversed from where you're standing) at some layer within Turf to make sure the output is valid geojson.

If you don't want your result wound according to the spec, it might be of help to note Turf has a rewind() function that includes a reverse option.