The text is explicit that it is not teaching the eight limbed yoga of the classical tradition, and the difference is structural rather than terminological. It sets out seven stages, beginning with cleansing procedures for the body, then hardening, then steadying, then the steadying of the mind, then lightness, then perception, then isolation, and it calls the whole thing the yoga of the vessel. The vessel is the body, understood as a pot that must be fired before it will hold anything. That image governs the arrangement. Purification comes first because an unfired pot leaks, and the postures belong to the third stage, as a means of making the body steady rather than as the discipline itself.
Nothing in the sequence corresponds to the ethical restraints and observances that open the classical eight limbed scheme, which is a substantive difference and not an omission. The framing is a teaching dialogue: a questioner asks and the sage answers, a form that lets the text present a complete curriculum in order without having to argue for any part of it. Read alongside the other classical hatha manuals, which cover much of the same ground in a different order and under a different scheme, it shows that the tradition contained more than one way of organising the same practices, and that the eight limbed model people reach for first is not the only one it had.