May be im miss smth, but look at this code, please:

$from = $date_handler->sql_where_date('DATE', $from_field, '<=', date_format($max_date, $format));
$to   = $date_handler->sql_where_date('DATE', $to_field, '>=', date_format($min_date, $format));

file date_api_argument_handler.inc at line 351
If we got content with this date: from: 2009-10-08 to: 2010-06-12,
And use this argument 2010-03-02--2010-03-03
Then this is true:
2009-10-08 <= 2010-03-02
2010-06-12 >= 2010-03-03
But in logic this must look like this:

2009-10-08 >= 2010-03-02
2010-06-12 =< 2010-03-03
if code would be this:

$from = $date_handler->sql_where_format($format, $from_field, '>=', date_format($min_date, $format));
$to   = $date_handler->sql_where_format($format, $to_field, '<=', date_format($max_date, $format));

Sorry for my english