It depends on your definition of psychedelic then, as I find different sources supporting either argument, but NO2 produces powerful hallucinations, euphoria, dissociation, and sometimes creativity much like typical psychedelics, but on a compressed timescale.
It's common to distinguish between "psychedelics", which primarily function via serotonin receptors, and "dissociatives", which primarily function via NMDA receptors.
The term psychedelic is describing specific subjective effects rather than a mechanism of action, what you're thinking of are the classic serotonergic psychedelics which are 5ht2a agonists but ketamine and other dissociatives can be considered dissociative psychedelics
I’ve heard that Ketamine is a psychedelic deepener more than a psychedelic on its own. Ie, a little ket addition is similar to taking a much higher dose of psychedelics (but short duration): high definition mental imagery and expanded external visual effects. With a good set & setting, that combo nearly guarantees a mystical experience.
A compound that can deepen a psychedelic experience can also be a psychedelic on its own. There are people who like to smoke DMT during the peak of an LSD experience because of this deepening but both are capable of producing mystical experience on their own, just as ketamine (especially the S isomer) is capable of
