According to Osho, Kundalini sadhana works in the psychic realm—the subtlest form of matter (breath, mind, psyche)—and is not itself spiritual. Like a diving board, it prepares the right state and becomes a stepping stone from body-mind to soul. The spiritual is attained only when, from that prepared base, the 'jump' beyond mind and energy actually happens.
Kundalini practice tunes your inner energy so you can leap into spirit; the energy-work isn’t the spirit itself.