It is best to forget about "non-conceiving" altogether, instead think it of wise-conceiving.
i.e. to wisely regard all conditioned things as ultimately impermanent and unsatisfactory, and all things including Nibbana as not 'I' or 'mine'.
Then conceiving will occur naturally when it is necessary, and non-conceiving will occur when it is adequate.
(Also please note, MN 1 was for sons of Brahmins, who were used to being segregated into 4 classes.)