All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
What you have read in our fatwas is correct, and there is no contradiction between the texts which you mentioned and what we stated in our fatwas. What you mentioned indicates that the basic principle is that the daytime should be for work and the night should be for sleeping and rest.
However, there is no reported forbiddance of sleeping during the daytime or staying up at night. What was reported in this regard is that the Prophet, sallallahu ‘alayhi wa sallam, disliked conversation after performing the ‘Ishaa' prayer, as is cited in Saheeh Al-Bukhaari. This clearly proves what we have previously stated, that staying up at night is disliked and not recommended. However, a person does not bear a sin for it if he is carrying out his duties and tasks at night. In fact, staying up at night could be praiseworthy if it is spent in carrying out an act of obedience such as studying or discussing knowledge, performing the night prayer, or the like.
Allah knows best.