A filter applied to the label of the outlinks action parameter is only applied to the first subsite, not to the other ones that are queried at the same time and when a date-range is used.

Works:
Only one site, date range

?module=API&method=Actions.getOutlinks&idSite=2&period=day&date=previous7&filter_column=label&filter_pattern=download&format=xml

Works:
multiple sites, single date

?module=API&method=Actions.getOutlinks&idSite=all&period=day&date=yesterday&filter_column=label&filter_pattern=download&format=xml

Does _not_ work:
multiple sites, date-range

?module=API&method=Actions.getOutlinks&idSite=all&period=day&date=previous7&filter_column=label&filter_pattern=download

result is that the output is filtered for the first site only. The other sites return the results as if the filter was not specified. (No difference when using filter_column_recursive and filter_pattern_recursive instead)
Keywords: actions api, filter, multiple sites, date-range