Spot colors are defined as extra print channels / extra inks. This is the definition and the most common use (precise terminology: spot colors used as process colors). Next to this spot colors are often used to name a color (precise terminology: named colors). The PDF model does not have a distinction between them and considers all spot colors as process colors so that areas that are covered with 2 or more (spot) colors are showing the correct overprint. This can be seen in the production preview of Adobe Acrobat.

The Editor takes the behavior of Adobe Acrobat as default and adds (up to 24 channels) as process colors to the document. When the user doesn’t want them as process colors he/she should click “convert to process” in the channels palette:

 

When the user want to add the spot colors in the document to the color list he/she can check the option “Convert spot colors to named colors” at opening the document: