Those are triggers and not conditions, even if a trigger triggers at the same exact moment, which will never ever happen, they will never activate the same part and thus not fulfill the ALL condition.
Hence you need to add conditions (AND cards):
[IF] motion deactivates [AND] both sensors’ motion alarm is false (this needs 2 cards, one for each motion sensor) [THEN] turn light off.
Or a better option is using the zone activity for this, as the zone is and stays active as long as one or both motion sensors are active.