What's the point on using KF in addition when loading datastore objects?

Hi all,

i'd like to know why sometimes KFs are uploaded in addition even when loading a dso.

I mean, when KF are all in overwrite it's easier to do a full repair request if something goes wrong or you are loading a new field in BW, so why some KFs are in addition (stock movements for example)? It's a choice or it's mandatory?

Thank you

Stefano