An emphatic (muʾakkad) simile omits the overt comparison particle; an explicitly marked (mursal) simile includes one. This division concerns expression of the particle, not whether the resemblance is familiar or remote.
وَهِيَ تَمُرُّ مَرَّ السَّحَابِ
And they will pass like the passing of clouds.
In Qur'an 27:88, the mode of passing supplies the resemblance even without the common particle “ka-.” Omission may make the resemblance appear more closely integrated with the description.