Created attachment 3511 [details] [review]
There is no point to this. Koha discards the selection because it can't translate between MARC21 and UNIMARC. That box should actually contain options for character encodings, not MARC formats (see related bug 5859).
This bug is mentioned in:
Bug 5997 : Use marcflavour in Stage MARC Records For Import http://lists.koha-community.org/pipermail/koha-patches/2011-March/014330.html