Couldn't find anywhere else to file a bug, so here I am...
The Esri coordinate system definition 54002 ("World" > "Equidistant Cylindrical") uses the spherical variant of the Equidistant Cylindrical projection. However, it also uses WGS 84 (an ellipsoid) as its Datum and is categorized in the ellipsoidal coordinate systems. The fact it combines the spherical projection with an ellipsoidal datum causes problems when reading shapefiles exported from ArcGIS in other GIS applications that support the two variants.
54002 should be using the ellipsoidal variant of the Equidistant Cylindrical projection (i.e. "Equidistant Cylindrical Ellipsoidal"). That way, when exporting .prjs, the projection is defined as "Equidistant Cylindrical Ellipsoidal" and other applications that support the variants will use the correct formulas.
On a related note, exporting a map that uses either of the two variants of the Equidistant Cylindrical projection to a GeoTIFF will write out the projection in the file simply as "Equidistant Cylindrical". Because there is no differentiation between ellipsoidal and spherical, other applications always interpret it as the spherical version, which causes the georeference of the image to be shifted from its true position. Can you please fix the writing of .wkts to include the projection variant?