The MagickWand interface is a new high-level C API interface to ImageMagick core methods. We discourage the use of the core methods and encourage the use of this API instead. Post MagickWand questions, bug reports, and suggestions to this forum.
Most metadata associated with a JPEG image is stored as an EXIF profile. ImageMagick only updates a few fields such as the resolution and orientation. Use exiftool to update any additional metadata.
The rendering intent metadata doesn't seem to be exif related.
Also identify shows the rendering intent tag when no exif data is in the image at all. exiv2 doesn't allow to set rendering intent, too.
So it seems I have to look at a different place, any ideas?