According to Osho, 'Vasudeva' here is Krishna’s self-reference in the language Arjuna can grasp—the personal, visible form—not the ultimate formless reality. It’s a compassionate, pedagogical concession, an intentional “error” adopted to communicate with a beginner. Through this provisional term Krishna leads Arjuna step-by-step, later unveiling the Virat and paratpara Brahman beyond all names and forms.
Vasudeva means Krishna talking in a simple, personal way so Arjuna can understand, not the final formless truth.