Ezekiel experiences a profound moment of clarity, bridging his current divine revelation with his very first prophetic vision. The primary approach among commentators is that the prophet recognizes with absolute certainty that the heavenly beings before him are the exact same creatures that formed the divine chariot he previously saw by the river Chebar. However, he now reaches a new understanding of their true nature, realizing that they are cherubim.
This insight comes to him despite a distinct change in their appearance. In his first vision, one of the creatures had the face of an ox, but now the face of a cherub appears in its place [מצודת דוד]. It is exactly this transformation that leads the prophet to the absolute conclusion that the beings from his earlier vision were actually cherubim all along. Because the face of the ox was replaced, a highly unique image is created. The creature now possesses two distinct human faces: the small face of a child, which represents the cherub, alongside the larger face of a mature adult [רש״י].
Ultimately, recognizing these heavenly creatures as cherubim serves a specific purpose. It directly connects the spiritual beings of the divine chariot seen in the vision to the physical cherubim that stand inside the Temple [ביאור שטיינזלץ].