The Gita talks of three purushas too, but it does not refer to these as stages or realisations of the “individual”? Or does it? I always looked at the triple purushas of the Gita a little differently. Your clarification will help.
The three stages through which the Purusha discovers and recovers himself are the physical, vital and mental Purusha with corresponding physical, vital and mental personalities. During its identification with these three it is the bird tasting the sweet, bitter fruits. Turning away and knowing itself as the bird sitting above the nature it tastes its own delight.
Affectionately,
Alok Da