Groove Agent 4 Drum Maps

I am having a hard time understanding the logic behind Groove Agent 4 drum maps. Why are drum sounds such as “Fill n” or “Main n”, where in is an integer, often play snare, hihat or other instrument sounds as opposed to just mapping them to the instrument. It makes it difficult to edit drums. This occurs on many of the Drum Kit Patterns in Groove Agent. I am running Cubase 14 Pro if that matters.

Thanks