Непонятно поведение LIST

SELECT
...
    list(distinct cbd.date_receipt, ', ') date_receipt
FROM
    wp_supply_cardboard_itm cbd
LEFT JOIN wp_supply_cardboard_woff cbd_woff ON (cbd_woff.supply_cardboard_itm = cbd.id) and (cbd_woff.stock = 2)
group by 
...
having sum(cbd_woff.amount) <> 0