This is more of an annoyance than anything - but would be nice if it's fixable without a lot of trouble. Basically, the logic which takes the 'headerPattern' regular expression and matches it to column headers in an import file doesn't work for fields which are ID's - e.g. gender_id, suffix_id etc.
To recreate, import the attached file. Note that even though the "Gender" column header is an exact match to the headerPattern in Individual.xml - we don't get a match on the Mapping screen.