Emojis can be interpreted in different ways. The Unicode Consortium, which manages the introduction, removal and adaptation of 'official' emojis acknowledges this issue in their own guidelines. They state, emojis are 'encoded in Unicode based primarily on their general
appearance, not on an intended semantic.'
By virtue of their nature, any meaning given to emojis is flexible and open to misinterpretation. For example, historically many users have deployed the peach emoji to mean human buttocks. When this emoji was redrawn in 2016 to reduce its likeness to the human anatomy, a significant number of users complained to Apple that the critical 'second meaning' had been lost.
Emojis are therefore non-verbal cues insofar as they add meaning to written communication. However, they do not perform the same role as body language or intonation, as they have no fixed meaning.