Simile concerns not merely resemblance that may exist in reality but the way an expression communicates that resemblance. A speaker selects a quality and directs the listener to relate the two terms through that quality.
In “Khalid’s face is bright like the moon,” not every property of the moon is attributed to Khalid. Beauty or luminous appearance is the selected comparison, understood in a restricted respect.
Two people can be grammatical subjects of the same action without the speaker intending a figure of similarity. Reporting a shared fact and using shared quality to construct a simile are distinct communicative functions.