By default when you run a query for a hierarchical taxonomy term, WordPress also returns post from its children. This happen on backend and on frontend as well.
'tax_query'
argument has an argument 'include_children'
that was introduced for the scope, from Codex:
include_children (boolean) Whether or not to include children for hierarchical taxonomies.
Defaults to true.
So you should run a tax query to set that param to false, however is not possible run a tax query from a url, but you can act on 'pre_get_posts'
and set it.
See inline comments for further informations:
add_action('pre_get_posts', function( $query ) {
if ( // being sure the query is the right one
! is_admin() || ! $query->is_main_query()
|| ! ( $term = $query->get('ttc_catalogue') )
) return;
// being sure the page is the right one
$s = get_current_screen();
if ( $s->id !== 'edit-ttc_infobit' ) return;
// prepare tax query
$tax_query = array(
'taxonomy' => 'ttc_catalogue',
'terms' => array( $term ),
'field' => is_numeric( $term ) ? 'id' : 'slug',
'include_children' => FALSE
);
// set tax query
$query->set( 'tax_query', array( $tax_query ) );
// unset 'plain' ttc_catalogue argument
$query->set( 'ttc_catalogue', '' );
});