I can see you are trying to be clear but still a really confusingly worded question, broke my brain a bit. I think this might achieve what you want, but I’m not fully sure if I understand you correctly or not. Try it out anyway, it may or may not work:
$downloads_parent_posts = get_posts( array(
'post_type' => 'downloads',
'orderby' => 'title',
'order' => 'ASC',
'tax_query' => array(
'relation' => 'AND',
array(
'taxonomy' => 'download-category',
'terms' => $term->term_id,
'field' => 'term_id',
'include_children' => false
),
array(
'taxonomy' => 'download-category',
'terms' => get_term_children($term->term_id, $term->taxonomy),
'field' => 'term_id',
'operator' => 'NOT IN',
)
),
) );