Absolutely not true, the newest Science - research says we have internal clock´s ( due to Earth Magnetic Field and Sun/Moon) the work better then anything else the old Q-Gong Masters new this since thousend´s of years that´s why when they really wanted to get best results from training they had to start training at three in the morning.
The most healthy sleep is till midnight if you have debiliating illness try to go to sleep at 20:00 and get up early sometimes geting up then at three in the mornig and taking meds/remedies is very good.