Quite the opposite my confused friend.
If the plant is always producing sugars then it cannot focus on one thing at a time. They will produce sugars and try to use them at the same time they are storing them, along with so many other processes of a plant.
If the plant is given time to 'rest' and use the sugars it has produced during the 'day' cycle then logic would dictate that during the 'night' cycle they would focus on growth.
Seriously, open a BIO 101 book.
Tried and tested, mother approved!
E